Why would he need to do that? He isn't some hobbyist, he has worked for actual toy companies where he painted resin castings to serve as prototypes multiple times. He wasn't even scratching here, he barely had to try to peel it.
@@JohnJones-oy3mdit isn't me white knighting, it is me being annoyed at people asking him to do something there is no point in. He literally showed some he had made for professional work in his last video.
Is it possible that the old elephant mold had residual release from your prior example and that ended up on the pull? Perhaps a you need to test on a new fresh mold and then try the Mann release? Also, could you fingernail test another part that is produced WITHOUT using mold release / painted using your normal procedure?
I put some Dawn dish detergent on a toothbrush and scrub my casts. (It is specifically formulated to wash away grease and oils.) Then I rinse the soap out of the toothbrush and scrub again using running water to remove soap residue. Once dry I spray with a clear “adhesion promoter” that mentions plastic or fiberglass on the label from an auto parts store. When I paint, I use craft acrylics that claim to be intended for “multi-surface” use including plastic, at least as the base coat. The bond will never be as strong as a factory paint job involving heat and specially formulated industrial paint, but it is sufficient. It may seem like an lot of steps, but when performed in an assembly line manner with multiple casts, I believe the time spent while using a release to extend mold life is better than the time and expense of remolding. Other artists I know prefer a thin dusting coat of crystal clear or matte finish spray instead of adhesion promoter, but I have never bothered trying it, because what I do works. In my experience, gesso is intended as a primer on porous surfaces, such as canvas. Thinning any acrylic type paint like gesso with water will make it more likely to bead up on a smooth surface, one must experiment to find a happy medium between thinner consistency good coverage.
I dont have a pressure pot (only a diy vacuum chamber), because Im making casting of my own sculpts (mostly historical tabletop minis) and the small parts can be very challenging Im using talcum powder. This doubles as release and (mostly) a way to ensure that via capillary action the resin will fill all the details without bubbles. At least in theory. I was thinking about using the exact same mold release since many people praised it and even said that it prevents catching bubbles. Robert you saved me 30 euros with this video. Thank you! I would like to see you trying the talcum powder for a video.
"Bonds to plastics" means eats into soluble thermoplastics. Resin is extremely resistant to solvents. So mechanical bonding it is. Can be helped by light sanding if there are problems.
I've used simple green to remove mold release. I don't recall a problem like this. I also had an old timer suggest a light bulb bake for resins (80 watts in a cardboard box) to get the resin to release surface oils. Clean twice once before and after the bake and acrylic seemed to stick fine. No clue how well that works with current formulations. I haven't painted resin in quite some time but gives me a hankering for making a garage kit again.
😳The look on my face when you peeled the spray primer off after using the EXACT mold release I use and the EXACT method of cleaning! I don’t really use mold release a whole anymore (just special cases) but now I’m really worried about some earlier pieces I’ve made haha!
I use that same mold release and never had any issues with paint pealing off like that. It could be old residue left behind on the mold. Rust-oleum paint and primers are what I spray them down with and leave for a full 24 hours to fully dry before doing anything and it takes a heck of a lot to scrape any paint away if it got onto a spot I didn't want (like if it made it into a clevis of a taped off portion) so to see it peal off as easily as it did here tells me it's more likely some other residue left behind on the mold or something is jank with the resin you are using.
I've tried that exact release, had the same issues. All I do now is either no release, or I lightly dust the molds with talc then blow most of it out with my air compressor. That could just be a legacy practice/habit though, since before I had a pressure pot the talc always seemed to help pull the resin into the fine details and eliminate bubbles.
When spraying or brush painting on plastic it does help to let it dry for a few hours before scratching it or testing adhesion. It will always peel when wet. Let it cure and it would prob be fine, especially the spray made for plastics.
Only time I've _used mold release_ is when I have to *cast* RTV into RTV _molds_ or certain types of *_urethane_* resins which stick like _crazy_ to everything. In some *very rare* cases I've actually used talc _but that_ was for low temp metals. Otherwise, I hate mold release. It *removes* detail and is a _general_ pain to use.
I wouldnt have used soap and water, myself. I always clean with something stronger like acetone. I want my pieces to be handled after the paint has cured. Pretty sure the spray paint cures strongest in about 7 days (who has time for that! But, I do seem to recall that being the case). Might be best to wash with something stronger and anneal the casting if using Gesso. You're right to stay away from it if it causes this much extra work.
I also dislike Ease Release. I have stuck more parts with it than with any other release system I have tried. It is silicone, and it leaves a matt finish. Maybe the matt surface helps with some mechanical bonding to the part? But I want a gloss finish, and I don't wan't to be worried about stuck molds! (Obviously sticking a part isn't a problem if casting with silicone molds, but I'm casting urethane in rigid fiberglass molds, so sticking is always a danger.)
I painted a lot of resin oder metal figures, but I use Vallejo oder AK Interactive Primer through an Airbrush. And let IT cure over night. I usually let the figures take a bath in an ultrasonic cleaner with Soap water. And I'm sure they all had some mold release on them. Before going in the ultrasonic, sometimes even superglue isn't sticking to them.
I remember using a soft bristle tooth brush and dish soap. Dont think I've had an issue after a good cleaning. More effort, but sometimes its worth it, i guess
Like Theexplorographer meantioned, an alcohol bath is usually what we in the miniatures world uses. We all have been steered that direction, or using LA's awesome or mean green. I have not tried this product, so I cannot say. My suggestion would be to try alcohol.
Your video is perfect for UA-cam. I've had my can for years and never bothered to look on UA-cam for Mann Mold Release 200 and painting. I received my info. from the Smooth-On distributor in my area. I cant see anything on UA-cam showing this in practice. I'm not seeing any retailer indicating removal with soap and water prior to paint and addressing any adherence issues. Cant believe no one else has put a video showing the claim in action. Maybe my search terms are off but I'm not seeing it.
Robert, Use Mean Green or Pure 90% alcohol for your wash. Also, I have had great luck with an ultrasonic cleaner and mean green. 2 mins in the bath, dry it and boom, ready for paint. And honestly, most of us are using spray primer.. Most mold releases have silicone in them. Gesso and silicone equal a fleeing event in the paint as you are experiencing. In fact, when doing acrylic pour painting, we often use silicone to make the designs because the paint flees from the silicone areas. Basically, water and oil don't mix. A reaction similar to that is what you are experiencing here. Because of nature of mold release you are going to have to go harder than soap and water, or like you say, just don't use it. 😉 Horse dead, and beaten.
Smooth plastic or smooth resin-based items can have the same result without mold release. I've had the same result painting styrene with Gesso. A lack of a keyed surface or anything for a water-based product to grip can lead to a peal. Even some solvent-based primers will peel from smooth surfaces. Plastic bonding primers work fairly well but can still have problems with smooth surfaces.
Who has time to wait for mold release to dry? What if it's a mold you can't get it in? I don't use mold release either. If I need it colored, I use powder pigments on the inside of the mold. It's the same stuff paint is made out of, so it doesn't turn yellow or fade.
Maybe paint will stick if you have a silicone additive in the paint? There are products designed to prevent fisheyes when refinishing wood that has been exposed to silicone.
It’s possible that this particular moldrelease is not water soluble maybe it needs an isopropyl alcohol bath and scrub. But I get it you’re adding more processing time to each piece you cast.
Hi, I was wondering how you built your custom pressure pot if you wouldn't mind sharing? The concept and material seem pretty straight forward and simple having the know how with plumbing, pnuematics, and welding but i wanted to know if there was maybe something you learned from making them or any tips/tricks. Want to build one for my wife.
Hi Robert and other mold experts. I’m new to mold making and have binge watched several of the videos here. I love this channel….it’s both educational and entertaining. I have a project where I want to create a silicone mold of a real dried (dehydrated) pumpkin stem so I can cast resin replicas of it. Can I create molds from organic materials like pumpkin stems? Do I need to put some kind of coating on the stem first like vegetable oil or something to prevent it from sticking to the mold? I don’t want to ruin the original stem I plan to use to create the mold.
Mr Tolone, have you tried spraying primer directly onto the mold? That's what Ive been doing and it seems to work great. It protects your mold, since the resin is physically not touching it, As the resin sets the primer chemically bonds onto it, making it almost ready for paint work right out the mold. It also prevents air bubbles building on the outside surface of the casting. Was never a fan of mold release either.
Dude what, that’s like black magic. The cure doesn’t effect the hold on the primer at all?? Obviously you shouldn’t be going wild with touching a paint job but I would love to know what the oldest item you have made and painted using this method.
What you are doing is essentially applying a barrier coat. Many resin suppliers sell barrier coats specifically for this purpose. I don’t bother with them on small castings but they have been useful for me when casting large objects. I should do a video just on barrier coats.
I was thinking about this over the past few days because I use this mold release myself and after a wash I've never had problems with paint not adhering to the casts, and I realized I powder my molds, I don't have a pressure pot so I need to take any extra help I can get, I'm wondering if that may be the barrier to make them paintable? It might explain the results some others are getting as well.
question-- I have trouble getting primer and gesso and paints to stick to resin with OR without mold release lol. Is there any paints that should be good for just plopping onto resin?
There may be, but I have never found one. I have always gotten good results from primer on resin followed by regular Artist acrylics. I do think it is important to measure the resin A/B ratio precisely.
Robert, I know you are a huge fan of the ye old wittnes cup. But as resin tends to cure slower in those thin layers. Have you ever had a casting that differed from the cup?
Good point, if there is only a thin film of resin left in the witness cup your casting will almost certainly cure faster. The other flaw of witness cups is that the resin on the bottom or sides may not be mixed as thoroughly as the main mass of resin. But I often demonstrate the method anyway, because people ask me how they can be sure that the resin is cured while it is inside the pressure pot.
Would sandblasting work? I've seen people make some very cheap DIY blasters and I was wondering if it'd be able to clean the mold release off and make the piece abrasive enough for painting?
🤔 Not to doubt your years of experience, but I was a little disappointed in either video you didn't do a control with an un-moldreleased part. Could it be that your resin is just too old? I've gone through hell trying to get spray paint to stick to my resin only to discover it was the old resin causing the issue. I switched to fresh and the paint stuck wonderfully.
I am not so sure you have more to learn than the audience does hahahaha. There may be thousands of us, but we have expertise ranging from "I know what I am doing in my specific resin casting application but not beyond that" to "I read some posts on reddit and they must be true". Your first video was correct, you do not need mean green, a 30 minute nonsense wash cycle in some fancy resin casting washing machine, or some alcohol mixture.... You just need to trust your actual years and years of expertise and not use a release agent.
I would suggest trying a different paint, for smooth on brand resin Ive had good adhesion with Tamiya brand paints with no primer. (I also use the smooth on universal mold release) Ive tryed using Vallejo brand paint, both the paint and primer for that brand didnt stick at all. I even tryed rustolum auto primer and that didnt stick. I'm sure it has to do with the chemical make up of the paint and it matching well with the resin more then anything. I'm sure calling the manufacture or a distributor would give better insight
Primers require a lot of hours to cure (they use resin in itself). Because they use resin (the one you used contained PU resin, whereas wall primers contain epoxy resin), well, you know that resin requires time to cure, right? ;) Some can take 8 hours, some can even take more than 24 hours, depending on the brands.
@@DKarkarov well my answer is based on mini painting, and most of our primers take a long time to cure. I dunno about the 1 hour part. It may be true, but remember that different materials also require different duration also. Rusteolum is not primarily used for PU resin so results may vary depending on the materials it is used on. Some materials are just so hard for the primers to stick to so waiting for a relatively longer time may be safer. It still requires trial and error, ofc
A lot of "what about trying..."in these comments. I doubt the man wants to try "just scrubbing a little harder" or "painting the mold first" or "using solvent X" or "baking the part first" or "using an ultrasonic cleaner" or...
Hmm, acrylics straight onto resin is not ideal even after a good clean. One should prime resins with an automotive etch primer or lacquer primer like Mr Surfacer. Cleaning mould release off is still essential ideally in an ultra sonic bath. Just my 2 pennies.
"IxNay Onyay oldMay eleaseRay"
Wise words by Robert Tolone
its pig latin
Bob , alcohol seems to be the consensus so the next round of beers on me .
Great experiments keep them coming !
Can you do a follow up video with no release used and do the same scratch test?
I concur.
Why would he need to do that? He isn't some hobbyist, he has worked for actual toy companies where he painted resin castings to serve as prototypes multiple times. He wasn't even scratching here, he barely had to try to peel it.
@@DKarkarov I'm sure Robert appreciates your white knighting.
@@DKarkarov I just think Robert does a great job at educating the community and it would be an interesting video to see.
@@JohnJones-oy3mdit isn't me white knighting, it is me being annoyed at people asking him to do something there is no point in. He literally showed some he had made for professional work in his last video.
Is it possible that the old elephant mold had residual release from your prior example and that ended up on the pull? Perhaps a you need to test on a new fresh mold and then try the Mann release? Also, could you fingernail test another part that is produced WITHOUT using mold release / painted using your normal procedure?
I put some Dawn dish detergent on a toothbrush and scrub my casts. (It is specifically formulated to wash away grease and oils.) Then I rinse the soap out of the toothbrush and scrub again using running water to remove soap residue. Once dry I spray with a clear “adhesion promoter” that mentions plastic or fiberglass on the label from an auto parts store. When I paint, I use craft acrylics that claim to be intended for “multi-surface” use including plastic, at least as the base coat. The bond will never be as strong as a factory paint job involving heat and specially formulated industrial paint, but it is sufficient. It may seem like an lot of steps, but when performed in an assembly line manner with multiple casts, I believe the time spent while using a release to extend mold life is better than the time and expense of remolding.
Other artists I know prefer a thin dusting coat of crystal clear or matte finish spray instead of adhesion promoter, but I have never bothered trying it, because what I do works.
In my experience, gesso is intended as a primer on porous surfaces, such as canvas. Thinning any acrylic type paint like gesso with water will make it more likely to bead up on a smooth surface, one must experiment to find a happy medium between thinner consistency good coverage.
I dont have a pressure pot (only a diy vacuum chamber), because Im making casting of my own sculpts (mostly historical tabletop minis) and the small parts can be very challenging Im using talcum powder. This doubles as release and (mostly) a way to ensure that via capillary action the resin will fill all the details without bubbles. At least in theory.
I was thinking about using the exact same mold release since many people praised it and even said that it prevents catching bubbles. Robert you saved me 30 euros with this video. Thank you!
I would like to see you trying the talcum powder for a video.
You are sooo right Robert you cannot paint anything on release spray it just rejects everything….. but thanks to you I always have my witness cup ❤
I always use mold release, wash it with soap and airbrush. Never had any issues with paint coming off.
Man I miss your project videos, I loved it when they were 3 parter videos
"Bonds to plastics" means eats into soluble thermoplastics. Resin is extremely resistant to solvents. So mechanical bonding it is. Can be helped by light sanding if there are problems.
The Elephant in the room happens to be the mold release!
I've used simple green to remove mold release. I don't recall a problem like this. I also had an old timer suggest a light bulb bake for resins (80 watts in a cardboard box) to get the resin to release surface oils. Clean twice once before and after the bake and acrylic seemed to stick fine. No clue how well that works with current formulations. I haven't painted resin in quite some time but gives me a hankering for making a garage kit again.
😳The look on my face when you peeled the spray primer off after using the EXACT mold release I use and the EXACT method of cleaning! I don’t really use mold release a whole anymore (just special cases) but now I’m really worried about some earlier pieces I’ve made haha!
I use that same mold release and never had any issues with paint pealing off like that. It could be old residue left behind on the mold. Rust-oleum paint and primers are what I spray them down with and leave for a full 24 hours to fully dry before doing anything and it takes a heck of a lot to scrape any paint away if it got onto a spot I didn't want (like if it made it into a clevis of a taped off portion) so to see it peal off as easily as it did here tells me it's more likely some other residue left behind on the mold or something is jank with the resin you are using.
I was feeling pretty hopeful after that second coat, but watching the paint just peel right away was so demoralizing.
I've tried that exact release, had the same issues. All I do now is either no release, or I lightly dust the molds with talc then blow most of it out with my air compressor. That could just be a legacy practice/habit though, since before I had a pressure pot the talc always seemed to help pull the resin into the fine details and eliminate bubbles.
As so one without a pressure pot you just saved me some heart ache
When spraying or brush painting on plastic it does help to let it dry for a few hours before scratching it or testing adhesion. It will always peel when wet. Let it cure and it would prob be fine, especially the spray made for plastics.
Only time I've _used mold release_ is when I have to *cast* RTV into RTV _molds_ or certain types of *_urethane_* resins which stick like _crazy_ to everything. In some *very rare* cases I've actually used talc _but that_ was for low temp metals. Otherwise, I hate mold release. It *removes* detail and is a _general_ pain to use.
I wouldnt have used soap and water, myself. I always clean with something stronger like acetone. I want my pieces to be handled after the paint has cured. Pretty sure the spray paint cures strongest in about 7 days (who has time for that! But, I do seem to recall that being the case). Might be best to wash with something stronger and anneal the casting if using Gesso. You're right to stay away from it if it causes this much extra work.
I also dislike Ease Release. I have stuck more parts with it than with any other release system I have tried. It is silicone, and it leaves a matt finish. Maybe the matt surface helps with some mechanical bonding to the part? But I want a gloss finish, and I don't wan't to be worried about stuck molds! (Obviously sticking a part isn't a problem if casting with silicone molds, but I'm casting urethane in rigid fiberglass molds, so sticking is always a danger.)
I painted a lot of resin oder metal figures, but I use Vallejo oder AK Interactive Primer through an Airbrush. And let IT cure over night.
I usually let the figures take a bath in an ultrasonic cleaner with Soap water.
And I'm sure they all had some mold release on them. Before going in the ultrasonic, sometimes even superglue isn't sticking to them.
I remember using a soft bristle tooth brush and dish soap. Dont think I've had an issue after a good cleaning. More effort, but sometimes its worth it, i guess
Like Theexplorographer meantioned, an alcohol bath is usually what we in the miniatures world uses. We all have been steered that direction, or using LA's awesome or mean green. I have not tried this product, so I cannot say. My suggestion would be to try alcohol.
Your video is perfect for UA-cam. I've had my can for years and never bothered to look on UA-cam for Mann Mold Release 200 and painting. I received my info. from the Smooth-On distributor in my area. I cant see anything on UA-cam showing this in practice. I'm not seeing any retailer indicating removal with soap and water prior to paint and addressing any adherence issues. Cant believe no one else has put a video showing the claim in action. Maybe my search terms are off but I'm not seeing it.
Robert, Use Mean Green or Pure 90% alcohol for your wash. Also, I have had great luck with an ultrasonic cleaner and mean green. 2 mins in the bath, dry it and boom, ready for paint. And honestly, most of us are using spray primer.. Most mold releases have silicone in them. Gesso and silicone equal a fleeing event in the paint as you are experiencing. In fact, when doing acrylic pour painting, we often use silicone to make the designs because the paint flees from the silicone areas. Basically, water and oil don't mix. A reaction similar to that is what you are experiencing here. Because of nature of mold release you are going to have to go harder than soap and water, or like you say, just don't use it. 😉 Horse dead, and beaten.
Self etch primer might work.
Smooth plastic or smooth resin-based items can have the same result without mold release. I've had the same result painting styrene with Gesso. A lack of a keyed surface or anything for a water-based product to grip can lead to a peal. Even some solvent-based primers will peel from smooth surfaces. Plastic bonding primers work fairly well but can still have problems with smooth surfaces.
Who has time to wait for mold release to dry? What if it's a mold you can't get it in?
I don't use mold release either. If I need it colored, I use powder pigments on the inside of the mold. It's the same stuff paint is made out of, so it doesn't turn yellow or fade.
Maybe paint will stick if you have a silicone additive in the paint? There are products designed to prevent fisheyes when refinishing wood that has been exposed to silicone.
It’s possible that this particular moldrelease is not water soluble maybe it needs an isopropyl alcohol bath and scrub. But I get it you’re adding more processing time to each piece you cast.
Hi, I was wondering how you built your custom pressure pot if you wouldn't mind sharing? The concept and material seem pretty straight forward and simple having the know how with plumbing, pnuematics, and welding but i wanted to know if there was maybe something you learned from making them or any tips/tricks. Want to build one for my wife.
ua-cam.com/video/Aro-CkdI6O0/v-deo.htmlsi=Qnc8N_91n1UDai3M
ua-cam.com/video/VYO318KFuAA/v-deo.htmlsi=UDGDzV1rOgDyp-Mz
Hi Robert and other mold experts. I’m new to mold making and have binge watched several of the videos here. I love this channel….it’s both educational and entertaining. I have a project where I want to create a silicone mold of a real dried (dehydrated) pumpkin stem so I can cast resin replicas of it. Can I create molds from organic materials like pumpkin stems? Do I need to put some kind of coating on the stem first like vegetable oil or something to prevent it from sticking to the mold? I don’t want to ruin the original stem I plan to use to create the mold.
no rinse?
Mr Tolone, have you tried spraying primer directly onto the mold? That's what Ive been doing and it seems to work great. It protects your mold, since the resin is physically not touching it, As the resin sets the primer chemically bonds onto it, making it almost ready for paint work right out the mold. It also prevents air bubbles building on the outside surface of the casting. Was never a fan of mold release either.
Dude what, that’s like black magic. The cure doesn’t effect the hold on the primer at all?? Obviously you shouldn’t be going wild with touching a paint job but I would love to know what the oldest item you have made and painted using this method.
What you are doing is essentially applying a barrier coat. Many resin suppliers sell barrier coats specifically for this purpose. I don’t bother with them on small castings but they have been useful for me when casting large objects. I should do a video just on barrier coats.
@@RobertTolone please please please!
I was thinking about this over the past few days because I use this mold release myself and after a wash I've never had problems with paint not adhering to the casts, and I realized I powder my molds, I don't have a pressure pot so I need to take any extra help I can get, I'm wondering if that may be the barrier to make them paintable? It might explain the results some others are getting as well.
Don't you have to leave the paint to cure before trying to scrape it off?
Ever consider an airbrush for mass painting or do you stick to rattlecans?
question-- I have trouble getting primer and gesso and paints to stick to resin with OR without mold release lol. Is there any paints that should be good for just plopping onto resin?
There may be, but I have never found one. I have always gotten good results from primer on resin followed by regular Artist acrylics. I do think it is important to measure the resin A/B ratio precisely.
got you robert, thanks!@@RobertTolone
Bob, I think instead of using an elephant, maybe you should have used a “pig”! Ha ha ha all in good natured fun…..
What, you don't usually use any primer either? I've had problems for primer sticking well to resins and you just leave it out.
Robert, I know you are a huge fan of the ye old wittnes cup. But as resin tends to cure slower in those thin layers. Have you ever had a casting that differed from the cup?
Good point, if there is only a thin film of resin left in the witness cup your casting will almost certainly cure faster. The other flaw of witness cups is that the resin on the bottom or sides may not be mixed as thoroughly as the main mass of resin. But I often demonstrate the method anyway, because people ask me how they can be sure that the resin is cured while it is inside the pressure pot.
Mold release becomes paint release.
Would sandblasting work? I've seen people make some very cheap DIY blasters and I was wondering if it'd be able to clean the mold release off and make the piece abrasive enough for painting?
Toss it in some nitroglycerin, that should take off the mold release.
🤔 Not to doubt your years of experience, but I was a little disappointed in either video you didn't do a control with an un-moldreleased part. Could it be that your resin is just too old? I've gone through hell trying to get spray paint to stick to my resin only to discover it was the old resin causing the issue. I switched to fresh and the paint stuck wonderfully.
" IxNay Onyay oldMay eleaseRay" Its pig latin if anyone is wondering.
I am not so sure you have more to learn than the audience does hahahaha. There may be thousands of us, but we have expertise ranging from "I know what I am doing in my specific resin casting application but not beyond that" to "I read some posts on reddit and they must be true".
Your first video was correct, you do not need mean green, a 30 minute nonsense wash cycle in some fancy resin casting washing machine, or some alcohol mixture.... You just need to trust your actual years and years of expertise and not use a release agent.
I would suggest trying a different paint, for smooth on brand resin Ive had good adhesion with Tamiya brand paints with no primer. (I also use the smooth on universal mold release) Ive tryed using Vallejo brand paint, both the paint and primer for that brand didnt stick at all. I even tryed rustolum auto primer and that didnt stick. I'm sure it has to do with the chemical make up of the paint and it matching well with the resin more then anything. I'm sure calling the manufacture or a distributor would give better insight
Primers require a lot of hours to cure (they use resin in itself). Because they use resin (the one you used contained PU resin, whereas wall primers contain epoxy resin), well, you know that resin requires time to cure, right? ;) Some can take 8 hours, some can even take more than 24 hours, depending on the brands.
Do they? Rustoleums data sheet for the one he used says 1 hour max.
@@DKarkarov well my answer is based on mini painting, and most of our primers take a long time to cure. I dunno about the 1 hour part. It may be true, but remember that different materials also require different duration also. Rusteolum is not primarily used for PU resin so results may vary depending on the materials it is used on. Some materials are just so hard for the primers to stick to so waiting for a relatively longer time may be safer. It still requires trial and error, ofc
A lot of "what about trying..."in these comments.
I doubt the man wants to try "just scrubbing a little harder" or "painting the mold first" or "using solvent X" or "baking the part first" or "using an ultrasonic cleaner" or...
Do it your way, and I'm thinking it will scratch off with your finger as well.
Hmm, acrylics straight onto resin is not ideal even after a good clean. One should prime resins with an automotive etch primer or lacquer primer like Mr Surfacer. Cleaning mould release off is still essential ideally in an ultra sonic bath. Just my 2 pennies.