Would love to see the same test with fresh resin since that is what many people would be using. This was interesting but was also testing a worst case scenario.
Agreed. A more realistic work scenario rather than the worst case scenario would be great imo. Especially for those who might not have the money or space for a heavy duty pressure pot. (Definitely wouldn't use a pickle jar though.)
20-45 psi is ok with fresh resin, recomend 45 psi, because when you use the resin from the bottle, that's when moisture contaminates your resin, and as you open the resin bottle cap the contamination will increase.
50 Psi is the pressure I use, just a rookie at mold making and resin casting but I have learned much from your channel. This is good stuff, thanks for sharing. Cheers!
This was absolutely interesting to see, Robert! Loved this one! I was thinking 75 lbs of pressure was going to be the number to shoot for, but 100 lbs certainly did the job!
"It's a big pickle jar", lmao, that one got me. :D Lovely video. I'm glad I saw a lot of your videos before I started casting! First two things I bought where a vacuum pot and a proper pressure pot with a compressor.
Your channel is absolute gold, Bob. Thanks so much for letting us have some of your shop time. You've saved me a lot of headaches and heartache on my current projects that include this type of work.
The universe has brought me to you to learn about molds. Currently that's where I am in this project that I am working on... the final part of specifically molding parts of it. Very cryptic I know. So I thought I'd be able to look up unique molding and figure out some different approaches... You share a lot of knowledge and wisdom that you compact in what at first glance might seem like a long video but at the conclusion is never quite long enough in my opinion. Thank you for all your hard work and for making my work much harder for now! I am looking forward to how much easier it will be.
You graphically demonstrated Boyle's law btw. For each 10psi, air will take up approx 50% the volume as its previous state. So, total volume of air at pressure: 10psi = 50% 20psi = 25% 30psi = 12.5% 40psi = 6.25% 50psi = 3.12% 60psi = 1.56%
YAY YAY. So I live in the mid-atlantic (us) and the vast vast majority of the time it is Very humid. However every once and a while it will dry out (to the x-tream). So when I was getting ready for my day and noticed that my sinuses felt like they were going to crack, I knew that I could squeeze all the humid-ass air out of all my resin bottles. Which since I still can't afford a press-pot/vac-chamber, is soooo helpful. I'm super excited for my next casting
Very interesting. I do buy in small amounts and would never have any that old and that full of moisture. I found 20-30psi is fine for stuff that isn't that old. I was surprised it took that much pressure to get it completely free though. Thanks for the vid.
The 25 PSI one (5:24) has quite small bubbles, the trouble is there were so much of them that they joined together and formed big cavities. So maybe if the resin wasn't foaming that much then only those tiny bubbles would be left.
Xtend-It dry gas blanket from Smooth-On is about $38 for a 10oz can and will last you a long time if you use small containers of resin. I've had the same can for over a year and haven't run out yet. I use a paint pressure pot at 50 to 60 psi and I get great results.
Well, I don’t know about the rest of you but I’m sticking with Bob. Bob knows resin casting. He’s proven it time and time again. If anyone doubts it, you’d be better off looking for a different channel. Best regards, Richard
I wonder if vacuuming the resin and hardener beforehand for significant enough time would allow the moisture that causes problems to evaporate? using Moisture trap of course
What I seen in those videos where they use vacuum is usually to remove air introduced while mixing resin. Some small lab chemical mixers were better than hand mixing but didn't remove need to vacuum. Not sure is same kind of resin because of safety gear what they used. Edit: They usually use transparent resin so you can see those bubbles even if they are small.
@@LimbaZero That's not the point. Good vacuum pump will have pressure that is less then partial pressure of water vapor at room temperature, so if you put water under vacuum it will start to boil (moisture trap is essential if you don't want to kill your pump). If you put your uncatalized resin under vacuum, it will dry and degass resin. You will always have bubbles appear under vacuum even when your resin is sitting undisturbed for a year. PS I cast with clear epoxy, have both vacuum and pressure pots, but epoxy is not a bit as reactive to moisture as polyurethane resin so I have very few bubbles without pressure as is (judging by leftovers, they never foam no matter how old is resin)
I’m afraid I am the one who asked Robert if I could use a pickle jar as a pressure pot many moons ago! But he set me straight and I listen to people who know better so I never did.
This is my world! My catalyst always hardens way before I use everything up. I always run at 80psi. I de-air my silicone and run it in the compressor as well (always using solid pieces with no porousness).
Thank you Bob , your awesome. Im brand new at all this. I started with 30 and went to 50 still catching air, but looks good. I got tons of stuff to ask but im going to keep watching more of your videos before i start asking lol... have a good one your friend Skillet
Great upload. Curious to see a proper guide to what is a good pressure pot to buy. There are so many for sale on Amazon but my gut feeling is I don't trust them, they are pressure vessels that need to be certified. I've seen pressure pots available from well known resin manufacturers, but they are overpiced, imho. Understand your workshop has a bespoke setup. Your view on a recommended pressure pot for small runs would be insightful.
I just got what most of us resiners use, a harbor fright pressure pot designed for paint. But you can remove the center rod, add a over pressure valve and use it as a pressure pot just fine.
Ouch! Heckling those without the funds for compression tanks and trying their best for strive for an alterative solution and then simply walked off screen in apparent disgust, disapproval, and frustration. In all the while I've watched you, I'm not sure I have seen you so dismissive. I've never seen you walk off the stage with a live camera before. You see people make loads of mistakes in sculpting, mold-making and casting and you seem so understanding and friendly and try to inform and educate people on the errors of their way and avoid being dismissive. OK, fine. I assure you that your message has been thoroughly received.
I know I will be lucky if you reply to my comment but I have something I would like to see you mold. Its a few parts from an articulated action figure. One of the parts(bicep) had a through hole that is mushroom shaped. Also another part would be the shoulder. A disk is trapped in the shoulder and this kind of molding I was told is insert molding with water soluble cores. Would love to see insert molding videos with this water soluble wax in action and how its done. Cheers and keep up the great videos, you're amazing! 🙂
Very important. If the mold wasn't created with vacuumed rubber, the pressure cast process can distort the mold due to the micro bubbles still in the rubber.
I don’t actually know. It is set by the factory on my compressor and I assume it’s somewhere above the maximum capability of the pump and below the failure point of the tank. The compressors I use tend to max out at around 125 psi. I never run them at maximum pressure because my pots are homemade and I don’t trust them!
If you're on a testing run, maybe give vacuuming the resin before mixing a try. Removing the moisture by boiling the water under vacuum. I think you can restore a bit of the quality of the resin with that, for sure still needing a pressure pot, but maybe 25psi might work. But to be honest, I run mine always at 60 psi, you can't over pressurize the resin.
@@RobertToloneno no, not curing under vacuum. Vacuum both resin parts separately to remove the moisture. Then mix the parts as usual and see how it cures. It should foam a lot less and might require less pressure in the pressure pot to get a solid result.
Id love to see how much the pressure differences in ultimate volume. Like, pour the exact same ml of resin into your cups and see if it crushes it smaller and smaller and highrr density / mold deformation and by how much
so many questions... 1, why not use a vacuum instead or pressure?? 2. can you use an inert gas like argon to flush a bottle before resealing it like wine people do?? 3. why do you side load instead of top load your pressure pots?? is that just their design?? thanks
I use vacuum in situations where it is effective but it is useless for preventing resin foaming. At the very end of this video, I link to another video I did about using inert gas. I also occasionally use a top-loading vertical version of my pressure pots for tall objects.
I only ever go up to 40psi when working with resin, 45 to 50 when working with silicone. That gives me crystal clear castings, even using completely clear resin. Anything less keeps bubbles within and anything over is just overkill.
Hello Robert, I have seen other resin users use a vacuum instead of added pressure for dealing with bubbles. Could explain why you chose pressure instead of vacuum to deal with bubbles in resin castings?
You often just don't need a vacuum, but a vacuum will always give the best results, and if you have unvented cavities it is required. It removes a lot of the gas that would cause bubbles and can fill even quite large unvented cavities, high vacuum combined with high pressure is guaranteed to leave no bubbles anywhere. I think some resins can start evaporating if the vacuum is too high though, which can make a mess of your pump.
@@samheasmanwhite Thank you. Based on some other commenters' answers, I also think that the type of resin might influence whether to use vaccum or not. I got the impression that epoxy resins have a longer working time than polyester resins. Thus epoxy would allow to get the mixing bubbles out with a vacuum prior to casting, whereas polyester resin might not give enough time to use a vacuum and then fill a mold before it starts to set. Thus the casting immiediately upon mixing and the use of pressure to shrink the bubbles.
I do that whenever I mix up some epoxy resin since it has such a long pot life compared to the flexible polyurethane resin that I normally use. Not sure if it makes any difference in the final castings or if it's the pressure pot that does all the heavy lifting, but it sure does bubble up under vacuum (about 30-35 Hg)
Is 100 psi enough to deform or crush a bit a soft mold like silicone? Or is that change enough to even notice? I'm wondering if there's a downside to using such high pressures for all castings.
The problem with trying to do that with softer materials is the when you release the pressure, the air bubble could expand again. That's why it's usually better to degas silicone and remove the bubbles before pouring.
I think the consensus is a vac chamber can be used, but is usually used for removing air from silicone before pouring for making a mould and the pressure pot/chamber for reducing bubbles in the resin. I'm sure Robert will have his own opinion.
Instead? No, it can be used alongside the pressure chamber, but maintaining pressure during cure is far more important. There's no way to guarantee your resin has no bubbles or gases in solution.
brillant, I used pressure of 100psi or even above that point BUT rubber molds tend to deform at high pressure rates like that. Wondered why ... Now for years I am fine doing my casting within a range of 30 to 50 psi of pressure. Anybody can try cheapo CLEAR polyester resin for testing (or even 5 Minute Epoxy glue) , does deliver pressure testing results very well and in tune with your equipment.
Rubber molds will deform at high pressure due to bubbles in the mold. Molds that are not made under pressure wont be able to hold up to it so its a good idea if you make molds to make them 5-10 psi higher then you would your resin casting. I cast my resin at 40psi, and molds at 45-50psi. Never had an issue deforming and get zero bubbles, even in clear resin.
Can you also test the affect of vacuum degassing the resin? I know you don't believe in degassing urethane as a rule, but this would be a great opportunity to settle the debate. It would be simple to cast 2 samples at 50psi and see if there is a difference in the amount of bubbles. I assume this is fast setting, so you'd have to de-gass the A and B separately before mixing...some people believe doing this is effective. I know that you will extract bubbles of something from both parts under vacuum, but I don't know what is bubbling and if it does anything good.
This is quite interesting. The degree of foamage would also presumably differ with the temperature of the resin. I don't know how much heat that particular resin puts out, which might make it pointless, but it would be interesting to see the same test with the resin chilled down. Lower temperature = higher gas solubility in the resin = maybe fewer bubbles? I'm a materials scientist by trade, and this looks like a great undergraduate lab exercise for understanding reaction kinetics. You could do the math and try to back calculate the activation energies of water within the resin from this data.
I am a Science fan boy, not a scientist. My experiences are purely anecdotal and non-scientific. When I hear the phrase “you could do the math” I run and hide in the closet!
@@RobertTolone For a non-scientist you have done an awful lot of really good science getting your processes dialed in. The type of work you have done (which, by the by, has been invaluable for me to learn from, thank you) is the entire basis of the field of engineering I do. This type of work is especially important to share because it is exactly not the type of thing you can learn from a text. You need to get your hands dirty. Thank you for all the inspiration and information.
Hi Robert, As you are my only reason that i start resin casting with silicone mold. I have a question. In our country the silicone rubber liquid is available is very thick and has low flow. What to add to make silicone rubber flowable. Some said use mineral spirit some said use silicone oil. But i will go with your opinion
This was super useful! Wondering, what's the smallest compressor and vacuum pump for small rooms with very limited space (no workshop) .. also what is the sculpting toy wax you use called?
Honestly I am always just confused why so many resin users seem to think the data sheet is some kind of joke. If your data sheet for the resin says "50psi is the ideal casting pressure" then you need to cast at 50psi. If you don't want to buy a pressure pot or compressor no matter what.... you need to use resin that has an extremely long cure time and is self degassing, and even then don't be shocked if a bubble still happens here or there.
What about using the foaming as a feature? I like building stuff that flies, how low can you get the density by promoting foaming and what is the best way to do so? Mix in water? How much?
What’re your thoughts on dry gas blankets? I get small bottles of resin at a time but I almost never use them up in one sitting so I thought about trying it. Although I always use a pressure pot so would the gas be unnecessary
Is it possible to run it at such high pressure that when you release the pressure, the internal pressure of the bubbles just overcomes the material strength of the resin and breaks the resin casting?
Why does it matter if there are bubbles in the resin not at the surface? If there are 1000 tiny bubbles inside the casting, why does that matter? I thought the whole point of suppressing bubbles is to keep them off the surface which causes defects in the final casting.
For one, material properties. The voids could serve as weak points, making the resin more brittle. Additionally, as you were able to see quite clearly, in one of the castings the bubbles amalgamated into large voids before the resin could solidify. Theoretically, if you could control bubble sizes and assure sufficieny toughness, it wouldn't be a problem, but we're talking small shop or homemade here. There's no engineering and/or QA teams on hand to guarantee it'll remain within optimal parameters. It's better to just operate with a wide safety margin.
@@WhenDoesTheVideoActuallyStart The structure doesn't matter when you are prototyping or you want to send it off to the company for approval or to serve as a model for an injection mold. I believe that is most of what he does, though he does do some small runs.
Because you will often see bubbles at the surface of the casting. Also, the foaming can distort and even force the mold open, resulting in a flawed casting.
Hey, Question here: Could i use the opposite, if i want to make epoxy foam insolation? I want to make a custom cooler. I already have a mold, but my experiments with EPS etc so far failed. Foamed up epoxy might be the solution?!?! Cheers
Something I wonder about. I assume you use polyurethane resin (surely youve mentioned it before but i dont recall.) since you talk about how its sensitive to moisture. It seems to me I see more people using Epoxy resin. So when someone says they pull low pressure and it cures just fine, Perhaps they are using a different resin than you. Maybe since Epoxy resin cures more slowly than polyurethane resin? I have no idea, Its just a theory since I dont use resin on a regular basis.
@@fredygump5578 it's a joke about the motto of the French revolution... But also where exactly is the freedom in large parts of the population working two jobs just to pay the rent? Don't bother I'm not really interested in a discussion comparing the US now with France in the 18th century😘
Please do another video that uses fresh, clear resin, so you can visually guage the effects of bubblage, and at the end, has a number (or range) that indicates a pressure that addresses the title of this video. Despite your good advice at the end, I don't really see the point of this video, and it seems you don't either.
The point is precisely that "how much pressure you need" depends on the situation, and it's just best practice to go for a more professional solution if you can afford it.
@@WhenDoesTheVideoActuallyStart You shouldn't be using bad resin. Good new resin is never going to do what happened in this video. The resin turned to foam because it was left open and absorbed a bunch of moisture from the air.
Would love to see the same test with fresh resin since that is what many people would be using. This was interesting but was also testing a worst case scenario.
Agreed, this would be a more helpful test. This one was interesting but worse case.
Agreed. A more realistic work scenario rather than the worst case scenario would be great imo. Especially for those who might not have the money or space for a heavy duty pressure pot. (Definitely wouldn't use a pickle jar though.)
20-45 psi is ok with fresh resin, recomend 45 psi, because when you use the resin from the bottle, that's when moisture contaminates your resin, and as you open the resin bottle cap the contamination will increase.
50 Psi is the pressure I use, just a rookie at mold making and resin casting but I have learned much from your channel. This is good stuff, thanks for sharing. Cheers!
Yeah I have the regulator on my pressure pot set at around 55-58 psi and I don't mess with it at all.
I love this channel.
I run mine at 60-65psi, no probs with that pressure for me.
This was absolutely interesting to see, Robert! Loved this one! I was thinking 75 lbs of pressure was going to be the number to shoot for, but 100 lbs certainly did the job!
Great video! I'd love to see more in the same vein.
"It's a big pickle jar", lmao, that one got me. :D Lovely video. I'm glad I saw a lot of your videos before I started casting! First two things I bought where a vacuum pot and a proper pressure pot with a compressor.
Your channel is absolute gold, Bob. Thanks so much for letting us have some of your shop time. You've saved me a lot of headaches and heartache on my current projects that include this type of work.
The universe has brought me to you to learn about molds. Currently that's where I am in this project that I am working on... the final part of specifically molding parts of it. Very cryptic I know. So I thought I'd be able to look up unique molding and figure out some different approaches... You share a lot of knowledge and wisdom that you compact in what at first glance might seem like a long video but at the conclusion is never quite long enough in my opinion. Thank you for all your hard work and for making my work much harder for now! I am looking forward to how much easier it will be.
You graphically demonstrated Boyle's law btw.
For each 10psi, air will take up approx 50% the volume as its previous state.
So, total volume of air at pressure:
10psi = 50%
20psi = 25%
30psi = 12.5%
40psi = 6.25%
50psi = 3.12%
60psi = 1.56%
YAY YAY. So I live in the mid-atlantic (us) and the vast vast majority of the time it is Very humid. However every once and a while it will dry out (to the x-tream). So when I was getting ready for my day and noticed that my sinuses felt like they were going to crack, I knew that I could squeeze all the humid-ass air out of all my resin bottles. Which since I still can't afford a press-pot/vac-chamber, is soooo helpful. I'm super excited for my next casting
Very interesting. I do buy in small amounts and would never have any that old and that full of moisture. I found 20-30psi is fine for stuff that isn't that old. I was surprised it took that much pressure to get it completely free though. Thanks for the vid.
Hey Randi - I just watched your apple carving video. It was great, you crack me up!
That was very interesting and informative, experience pays off. Thanks for sharing.
The 25 PSI one (5:24) has quite small bubbles, the trouble is there were so much of them that they joined together and formed big cavities. So maybe if the resin wasn't foaming that much then only those tiny bubbles would be left.
I'd love to see a comparison using a vac chamber as well.
Good to know this info! I expected ~30 to be the sweet spot.
That first cup of foam looks delicious...
Soufflé au Plastique
Delicious kitchen sponge
Forbidden cupcake
Xtend-It dry gas blanket from Smooth-On is about $38 for a 10oz can and will last you a long time if you use small containers of resin. I've had the same can for over a year and haven't run out yet.
I use a paint pressure pot at 50 to 60 psi and I get great results.
Well obviously we need to see a low pressure bike-pump-and-pickle-jar pressure pot test build and run some casting through it. For science. 🤣
What a great way to wright off old resin and put it to good use .👍👍👍
Great info!
Great close ups!
Well, I don’t know about the rest of you but I’m sticking with Bob. Bob knows resin casting. He’s proven it time and time again. If anyone doubts it, you’d be better off looking for a different channel.
Best regards,
Richard
I wonder if vacuuming the resin and hardener beforehand for significant enough time would allow the moisture that causes problems to evaporate? using Moisture trap of course
What I seen in those videos where they use vacuum is usually to remove air introduced while mixing resin. Some small lab chemical mixers were better than hand mixing but didn't remove need to vacuum. Not sure is same kind of resin because of safety gear what they used.
Edit: They usually use transparent resin so you can see those bubbles even if they are small.
@@LimbaZero That's not the point. Good vacuum pump will have pressure that is less then partial pressure of water vapor at room temperature, so if you put water under vacuum it will start to boil (moisture trap is essential if you don't want to kill your pump). If you put your uncatalized resin under vacuum, it will dry and degass resin. You will always have bubbles appear under vacuum even when your resin is sitting undisturbed for a year. PS I cast with clear epoxy, have both vacuum and pressure pots, but epoxy is not a bit as reactive to moisture as polyurethane resin so I have very few bubbles without pressure as is (judging by leftovers, they never foam no matter how old is resin)
thanks
I’m afraid I am the one who asked Robert if I could use a pickle jar as a pressure pot many moons ago! But he set me straight and I listen to people who know better so I never did.
I pre-vacuum the resin BEFORE I mix it, and I mix it very gently to avoid bubbles. Never had a need for a pressure pot.
This is my world! My catalyst always hardens way before I use everything up. I always run at 80psi. I de-air my silicone and run it in the compressor as well (always using solid pieces with no porousness).
Thank you Bob , your awesome. Im brand new at all this. I started with 30 and went to 50 still catching air, but looks good. I got tons of stuff to ask but im going to keep watching more of your videos before i start asking lol... have a good one your friend Skillet
Awesome video!
Great upload. Curious to see a proper guide to what is a good pressure pot to buy. There are so many for sale on Amazon but my gut feeling is I don't trust them, they are pressure vessels that need to be certified. I've seen pressure pots available from well known resin manufacturers, but they are overpiced, imho. Understand your workshop has a bespoke setup. Your view on a recommended pressure pot for small runs would be insightful.
I just got what most of us resiners use, a harbor fright pressure pot designed for paint. But you can remove the center rod, add a over pressure valve and use it as a pressure pot just fine.
THANK YOU !!!
Ouch! Heckling those without the funds for compression tanks and trying their best for strive for an alterative solution and then simply walked off screen in apparent disgust, disapproval, and frustration. In all the while I've watched you, I'm not sure I have seen you so dismissive. I've never seen you walk off the stage with a live camera before. You see people make loads of mistakes in sculpting, mold-making and casting and you seem so understanding and friendly and try to inform and educate people on the errors of their way and avoid being dismissive. OK, fine. I assure you that your message has been thoroughly received.
I know I will be lucky if you reply to my comment but I have something I would like to see you mold. Its a few parts from an articulated action figure. One of the parts(bicep) had a through hole that is mushroom shaped. Also another part would be the shoulder. A disk is trapped in the shoulder and this kind of molding I was told is insert molding with water soluble cores. Would love to see insert molding videos with this water soluble wax in action and how its done. Cheers and keep up the great videos, you're amazing! 🙂
I'm very curious to know how important vacuuming the rubber before making the mold is.
Very important. If the mold wasn't created with vacuumed rubber, the pressure cast process can distort the mold due to the micro bubbles still in the rubber.
@@Bren0780K ahhh, I see, thank you so much!
I really like the last 3 sec ;)😁
the beard of wisdom does not need to be to long.
I do wonder if there's a way to desiccate the moisture-ruined resin
Robert, this was a great comparison! Could you please tell me at what pressure your safety valves release?
I don’t actually know. It is set by the factory on my compressor and I assume it’s somewhere above the maximum capability of the pump and below the failure point of the tank. The compressors I use tend to max out at around 125 psi. I never run them at maximum pressure because my pots are homemade and I don’t trust them!
i use a vacuum for my resin its interesting that you use a positive pressure vessel.
I also use vacuum in situations where it is effective but it is useless for preventing resin foaming.
Could curing time help low pressure eliminate bubbles? For example, a resin that cures in 1 hour at a pressure of 25. Nice video!!!
If you're on a testing run, maybe give vacuuming the resin before mixing a try. Removing the moisture by boiling the water under vacuum. I think you can restore a bit of the quality of the resin with that, for sure still needing a pressure pot, but maybe 25psi might work. But to be honest, I run mine always at 60 psi, you can't over pressurize the resin.
The problem is that the resin I use sets up very fast and would cure under vacuum which makes the foaming bubbles bigger!
@@RobertToloneno no, not curing under vacuum. Vacuum both resin parts separately to remove the moisture. Then mix the parts as usual and see how it cures. It should foam a lot less and might require less pressure in the pressure pot to get a solid result.
Id love to see how much the pressure differences in ultimate volume. Like, pour the exact same ml of resin into your cups and see if it crushes it smaller and smaller and highrr density / mold deformation and by how much
so many questions...
1, why not use a vacuum instead or pressure??
2. can you use an inert gas like argon to flush a bottle before resealing it like wine people do??
3. why do you side load instead of top load your pressure pots?? is that just their design??
thanks
I use vacuum in situations where it is effective but it is useless for preventing resin foaming. At the very end of this video, I link to another video I did about using inert gas. I also occasionally use a top-loading vertical version of my pressure pots for tall objects.
@@RobertTolone thank you very much for taking the time to reply.
I only ever go up to 40psi when working with resin, 45 to 50 when working with silicone. That gives me crystal clear castings, even using completely clear resin. Anything less keeps bubbles within and anything over is just overkill.
Hello Robert, I have seen other resin users use a vacuum instead of added pressure for dealing with bubbles. Could explain why you chose pressure instead of vacuum to deal with bubbles in resin castings?
You often just don't need a vacuum, but a vacuum will always give the best results, and if you have unvented cavities it is required.
It removes a lot of the gas that would cause bubbles and can fill even quite large unvented cavities, high vacuum combined with high pressure is guaranteed to leave no bubbles anywhere. I think some resins can start evaporating if the vacuum is too high though, which can make a mess of your pump.
@@samheasmanwhite Thank you. Based on some other commenters' answers, I also think that the type of resin might influence whether to use vaccum or not. I got the impression that epoxy resins have a longer working time than polyester resins. Thus epoxy would allow to get the mixing bubbles out with a vacuum prior to casting, whereas polyester resin might not give enough time to use a vacuum and then fill a mold before it starts to set. Thus the casting immiediately upon mixing and the use of pressure to shrink the bubbles.
@@fredericapanon207 That makes sense yeah, but you might be able to use slower catalysts? At least I'm pretty sure you can get less reactive ones.
Cool test idea and thanks for sharing. Metric would be nice to see.
Are the bubbles the result of a chemical reaction? Or are they off-gassing like a freshly opened soda?
Robert, I noticed that no vacuum chambers were used in this video.........would putting the resin under vacuum help eliminate air bubbles?
I do that whenever I mix up some epoxy resin since it has such a long pot life compared to the flexible polyurethane resin that I normally use. Not sure if it makes any difference in the final castings or if it's the pressure pot that does all the heavy lifting, but it sure does bubble up under vacuum (about 30-35 Hg)
The bubbles that he is fighting in this video are formed while the resin is setting, you cant vacuum them before it starts to set.
Is 100 psi enough to deform or crush a bit a soft mold like silicone? Or is that change enough to even notice?
I'm wondering if there's a downside to using such high pressures for all castings.
The problem with trying to do that with softer materials is the when you release the pressure, the air bubble could expand again. That's why it's usually better to degas silicone and remove the bubbles before pouring.
I know it would be wasteful, but I'd like to see how fresh resin would alter the results.
I've seen using vacuum instead of pressure to get rid of bubbles. What say you?
I think the consensus is a vac chamber can be used, but is usually used for removing air from silicone before pouring for making a mould and the pressure pot/chamber for reducing bubbles in the resin. I'm sure Robert will have his own opinion.
Instead? No, it can be used alongside the pressure chamber, but maintaining pressure during cure is far more important. There's no way to guarantee your resin has no bubbles or gases in solution.
brillant, I used pressure of 100psi or even above that point BUT rubber molds tend to deform at high pressure rates like that.
Wondered why ... Now for years I am fine doing my casting within a range of 30 to 50 psi of pressure. Anybody can try cheapo CLEAR polyester resin for testing (or even 5 Minute Epoxy glue) , does deliver pressure testing results very well and in tune with your equipment.
Rubber molds will deform at high pressure due to bubbles in the mold. Molds that are not made under pressure wont be able to hold up to it so its a good idea if you make molds to make them 5-10 psi higher then you would your resin casting. I cast my resin at 40psi, and molds at 45-50psi. Never had an issue deforming and get zero bubbles, even in clear resin.
Hi! Thank you for the very informative videos) I wonder how thick is the walls of your pressure chamber?
I’d be curious to see the difference between a pressure pot and a vacuum chamber, on the bubble formation scenario.
Maybe you should be curious to read the instructions that come with your material and explicitly state not to vacuum degas it.
@@waytospergtherebro, interesting. I didn’t realize there were materials that specified pressure vs degassing.
Can you also test the affect of vacuum degassing the resin? I know you don't believe in degassing urethane as a rule, but this would be a great opportunity to settle the debate. It would be simple to cast 2 samples at 50psi and see if there is a difference in the amount of bubbles. I assume this is fast setting, so you'd have to de-gass the A and B separately before mixing...some people believe doing this is effective. I know that you will extract bubbles of something from both parts under vacuum, but I don't know what is bubbling and if it does anything good.
I think you should of marked the cup before you put in the pressure pot. What would you norm put the pressure up to on good resin?
How about resin dust?
This is quite interesting. The degree of foamage would also presumably differ with the temperature of the resin. I don't know how much heat that particular resin puts out, which might make it pointless, but it would be interesting to see the same test with the resin chilled down. Lower temperature = higher gas solubility in the resin = maybe fewer bubbles?
I'm a materials scientist by trade, and this looks like a great undergraduate lab exercise for understanding reaction kinetics. You could do the math and try to back calculate the activation energies of water within the resin from this data.
I am a Science fan boy, not a scientist. My experiences are purely anecdotal and non-scientific.
When I hear the phrase “you could do the math” I run and hide in the closet!
@@RobertTolone For a non-scientist you have done an awful lot of really good science getting your processes dialed in. The type of work you have done (which, by the by, has been invaluable for me to learn from, thank you) is the entire basis of the field of engineering I do. This type of work is especially important to share because it is exactly not the type of thing you can learn from a text. You need to get your hands dirty. Thank you for all the inspiration and information.
what if you degassed it first. how low could you go then?
Is this applicable to the rubber as well?
Hi Robert, As you are my only reason that i start resin casting with silicone mold.
I have a question. In our country the silicone rubber liquid is available is very thick and has low flow. What to add to make silicone rubber flowable. Some said use mineral spirit some said use silicone oil. But i will go with your opinion
This was super useful! Wondering, what's the smallest compressor and vacuum pump for small rooms with very limited space (no workshop) .. also what is the sculpting toy wax you use called?
Does epoxy resin have the same issues?
mine usually at 40-60 psi
Honestly I am always just confused why so many resin users seem to think the data sheet is some kind of joke. If your data sheet for the resin says "50psi is the ideal casting pressure" then you need to cast at 50psi. If you don't want to buy a pressure pot or compressor no matter what.... you need to use resin that has an extremely long cure time and is self degassing, and even then don't be shocked if a bubble still happens here or there.
What about using the foaming as a feature?
I like building stuff that flies, how low can you get the density by promoting foaming and what is the best way to do so? Mix in water? How much?
Just buy urethane foam. You cast it like any other resin, but it foams on purpose. And you can select what density you want.
@@fredygump5578 thanks, the options available to me are quite limited though :/ So exploring alternate ways of using materials sometimes pays off.
What’re your thoughts on dry gas blankets? I get small bottles of resin at a time but I almost never use them up in one sitting so I thought about trying it. Although I always use a pressure pot so would the gas be unnecessary
Nice title
One day I will be able to afford one
how about 3d printing a mold directly with TPU, its flexible, not rigid like PLA, one parts or two parts.
Excuse me but what’s the highest psi that your pressure tank can hold ?
To halve bubble size, you need 8x the pressure.
So yeah it will take a lot
Is it possible to run it at such high pressure that when you release the pressure, the internal pressure of the bubbles just overcomes the material strength of the resin and breaks the resin casting?
Why does it matter if there are bubbles in the resin not at the surface? If there are 1000 tiny bubbles inside the casting, why does that matter? I thought the whole point of suppressing bubbles is to keep them off the surface which causes defects in the final casting.
For one, material properties. The voids could serve as weak points, making the resin more brittle. Additionally, as you were able to see quite clearly, in one of the castings the bubbles amalgamated into large voids before the resin could solidify.
Theoretically, if you could control bubble sizes and assure sufficieny toughness, it wouldn't be a problem, but we're talking small shop or homemade here. There's no engineering and/or QA teams on hand to guarantee it'll remain within optimal parameters. It's better to just operate with a wide safety margin.
@@WhenDoesTheVideoActuallyStart The structure doesn't matter when you are prototyping or you want to send it off to the company for approval or to serve as a model for an injection mold. I believe that is most of what he does, though he does do some small runs.
Because you will often see bubbles at the surface of the casting. Also, the foaming can distort and even force the mold open, resulting in a flawed casting.
Hey, Question here: Could i use the opposite, if i want to make epoxy foam insolation? I want to make a custom cooler. I already have a mold, but my experiments with EPS etc so far failed. Foamed up epoxy might be the solution?!?! Cheers
I don’t use epoxy resins very much, and I don’t know whether moisture has the same effect on them. you would have to experiment and see.
@@RobertTolone thanks for the reply. By now i found a Pour In Foam, i ll try this and see if it works. Cheers
Something I wonder about. I assume you use polyurethane resin (surely youve mentioned it before but i dont recall.) since you talk about how its sensitive to moisture. It seems to me I see more people using Epoxy resin. So when someone says they pull low pressure and it cures just fine, Perhaps they are using a different resin than you. Maybe since Epoxy resin cures more slowly than polyurethane resin? I have no idea, Its just a theory since I dont use resin on a regular basis.
Somehow I thought you needed a vacuum to remove the bubbles but obviously the way your chambers are built you're using positive pressure.
Can we get the hypothetical pickle jar pressure pot guy on to do the test with his pot?
Like most of the world I only speak french revolution freedom units. What's that in Pascal?🤪
Are you up for a debate about who's version of "freedom units" are more free? Because 'Merica, obviously...
@@fredygump5578 it's a joke about the motto of the French revolution...
But also where exactly is the freedom in large parts of the population working two jobs just to pay the rent?
Don't bother I'm not really interested in a discussion comparing the US now with France in the 18th century😘
@@TheTutch I was making a joke about American's who have no self-awareness, because those are the ones who typically speak of "freedom units".
@@fredygump5578ah, I just assumed you were one of those exact same guys, because thats the ones I usually see in the comment section. My bad😅
Please do another video that uses fresh, clear resin, so you can visually guage the effects of bubblage, and at the end, has a number (or range) that indicates a pressure that addresses the title of this video.
Despite your good advice at the end, I don't really see the point of this video, and it seems you don't either.
How about breathing the fumes? how toxic is this stuff, I wear a auto body painting mask.
This was completely pointless. The question isn't "how much pressure does bad resin need," it's "how much pressure does resin I'm working with need?"
The point is precisely that "how much pressure you need" depends on the situation, and it's just best practice to go for a more professional solution if you can afford it.
@@WhenDoesTheVideoActuallyStart You shouldn't be using bad resin. Good new resin is never going to do what happened in this video. The resin turned to foam because it was left open and absorbed a bunch of moisture from the air.