For anyone curious, that green tape they are using is Polyester tape, it is typically used commercially as masking tape for powder coating or other high temp masking needs and has a working temperature range of -60°F to 400°F, and is also extremely resistant to chemical attack, it can be used in most solvents, acids and bases since it uses silicone adhesive (which is why it sticks to silicone) with a chemically resistant polyester backing. It is also very strong tape, it has very high tensile strength and can also be stretched to apply incredible tension if needed. It has hundreds of uses for hundreds of tasks, for a couple examples it can be used to make very thin but strong hinges on RC aircraft wing control surfaces, it is an excellent electrical insulator even for high voltage so is useful for all sorts of electronics projects, it can be made into incredibly detailed stencils if using a knife plotter or laser cutter, it can be applied to protect fine finishes on parts as it is extremely abrasion resistant and also leaves no residue behind afterward. And that's just scratching the surface, everyone who likes making stuff or doing craft hobbies should have at least a couple rolls of it laying around, it is beyond useful. It also comes in a huge variety of widths and thicknesses, I have at least two rolls of 1/8", 1/4", 3/8", 1/2", 3/4", 1", 2", 3" and 6" widths, and several different thicknesses of 1" and 2" rolls (arguably the two most useful widths) with the thinnest being about the thickness of a sheet of paper. It's not exactly cheap stuff but a little goes a long way.
Thank you for the info on the tape. May come in handy if I ever need tape that sticks to silicone molds. I've been doing pressure casting of resin in silicone molds for over 20 years. Noted a few things about the process with this mold which they're doing in much harder ways than they need to.
You can practically hear his passion for the art, and the respect he has for how these types of silicon castings were done previously! You can also see that he was pretty nervous in presenting at the first but as the filming continued, he got more and more comfortable and was able to match Adam's pace. lol
Worked nightshift in a production plastics fabrication factory in Brisbane, Australia. Vac forming signage for recognisable brands...acrylic lettering, light boxes, bullet proof money handling boxes... Amazing amount of woodwork for a plastics factory. All the moulds...wood. Frames, wood. Outlines, wood. Mockups, wood... Learned heaps working there...
I've been wondering for a few years if using vacuum casting for lenses is possible/practical! I'm glad to see that it is! The process shown here is FAR more detailed than what was in my head!
Jon seems like a good dude. Super interesting and clear, concise explanations. Im not in to cosplay or scifi etc but im fascinated by the process of moulding. Nice one!!
Am I the only person that thinks that if Adam decided to do a one day build that solved world peace, that not only would he do it, but he’d make a perfectly weathered box that it would fit in… he’s a national treasure!
Adam is great and does a lot of cool stuff and does great teaching stuff, but he’s as human as anyone else. He has all the same biases and flaws as the rest of us. It’s great to respect someone for their skill, experience and accomplishments, but just be careful about lifting them to super hero status.
Adam: "In the old days we just used to fill a mold with some resin and sit there and [pantomimes rocking the mold]." Jon: "Yeah, we don't do that." (dons full _Breaking Bad_ gear)
I don't know how expensive the professional silicone tape is, but I have used the bondage tape you can get in "adult fun stores" that "only sticks to itself" to tape silicone molds. The positive side to that is, that it is reusable if you don't cut it off and try to prevent too much dust from accumulating. .
Looks like the tape I used when masking off for powder coating. They use it as it's heat resistant to the 375F or so in the oven. Interesting if it also sticks to silicone.
I am assuming the adhesive is the secret sauce. I bought a version of this to test out. Caplugs High Temperature Masking Tape: 72 yd Long, 3.5 mil Thick, Green Polyester Film, Silicone Adhesive Mfr# SH-47520
Not Kapton, I think. The polyimide itself is what gives it that yellow/gold color. There are other polyester film tapes with a silicone adhesive for a reasonable price, I'm wondering if that is what makes the difference. Silicone adhesives might stick to a silicone mold.
They also do this in the auto restoration field. Taillight lenses for 70 year old cars simply don't exist. So they make them. 1. FIND a good one. If necessary, clean it up. They need to be good, but nobody is going to look through them. 2. Make the silicon mold. Much easier than here. 3. Fill mold with plastic stuff. 4. Put in tank, draw a good vacuum. 5. Pressurize the tank. 6. Wait, unmold. I'd bet someone does this on demand. Like that place in England that makes wiring harnesses.
The ending with Adam putting the lenses on his face and looking around reminds me of those joke scenes where a little kid wears a bra on his face in a similar fashion, not knowing what it is but pleased it somehow has that bridge for his nose that lets it fit around his face. >D
@AlexanderHenry-hz3td I don´t belive in any gods because humans use them as exuse to do harm to other people and feel good about it because it´s for their god
Yes. O'Neill's _High Frontier_ has a chapter on extracting and refining raw materials in vacuum. I'm sure the state of the art has moved on in the decades since.
I myself need to make a visor voor a helmet. But i am debating if I should vacuum form it, resin cast or a completely different method. Quite a riddle to solve
I've been looking forward to seeing this ever since you mentioned getting back from the UK! I love the elegant simplicity of this operation 🤌 I think you hit the nail on the head when you mentioned that this method just cuts out so much of the failure mode, of what this operation usually encounters.
how the hell do they put the tape onto the model? I mean... it must be placed on the model perpendiculary, like only with the super thin edge, right? oO Great video!
undoubtedly highly professional resin casting! i obviously am not working on your level but all that waste and extra effort (for those tiny lenses...) and a honest question to any fellow molders, casters or physicists in general: does a soft silicone mold, fully degassed, actually expand in the vacuum chamber? (3:35) since it maintains the same density regardless of durometer and doesnt compress in the pressure pot? And dont you get a LOT of expansion by heating the mold up "as hot as possible" (10:57)? Something doesnt add up here...
Hiya, professional vacuum caster here :) in answer to your questions: no a mould will not expand in a vacuum, the silicone is a homogeneous solid material and as long as it doesn’t contain large bubbles in it remains unperturbed by the vacuum. The molds can expand slightly with temperature, to keep this to the bare minimum a 40 shore silicone as in this video is typically cured in at 40 degrees centigrade (any hotter and 3D printed masters will distort!) Most resins we use require the mould to be heated to 70 degrees centigrade before use so that the resin will properly cure. We then typically cook the mould at 70 degrees for an hour or two depending on the resin used to properly cure it. Keeping the temps consistent is the key to producing parts as dimensionally accurate as possible.
Can someone explain the mold in the oven? When I froze the vid I think the oven read 68 degrees C. Is this peculiar to the plastic they were using? Thought it odd that they did not say what plastic they were using? Does the introduction of the chamber to vacuum alter the temp of the Part A and B in the chamber?
It think that is resin tape (PET tape with a silicone adhesive). I have seen that type of tape with acrylic adhesive on one side and silicone on the other.
Yeh that's such a better way to mold. I remember molding small master molds with my stepdad. We had the hardest time getting a good master molds of the little houses that he made. Too be cast in plaster. But the epoxy was terrible for defects. Didn't help with so much detail. I still have his first piece that was a solid piece of plaster he carved a castle out of. I would love to mold a master from, but I dare not Incase I ruin it. Any thoughts on this would be great. Thanks for the great content. Also Adam I have a bagpipe build you may be interested in collaboration with. It's right in your wheelhouse mate. Hit me up. I'll explain the concept. Much love mate.
I saw a post on Reddit where someone put resin into a vacuum chamber to degas it and it exploded everywhere and people were saying you cannot use a vacuum chamber for resin and must use a pressure chamber instead. Is that bad advice or what is the deal with resin in vacuum chambers?
If you have too much air in the mixed resin or pull the vacuum too fast all those little air bubbles in the mix will explode outward and make a mess. But you can easily vacuum resin even with lots of mixed in bubbles, it just takes time so needs to be a slower set resin (why they are mixing in the vacuum too here - no stirring in the air if there is no air to stir in, so it won't overflow the mixing pot as all the air bubbles grow). Helps alot if you can see through the chamber - then you can watch the rate the bubbles are making the whole thing grow and let air back in a bit and so apply the vacuum slow enough not to make a mess.
@@TheZahnputz but 1 bar is atmospheric pressure right? i used to do scuba diving and i was always told 1 bar is atmospheric pressure and 0 bar would mean a prefect vacuum.
@@downey2294 i think the confusion (at least mine) may orignate from using bar as a varibale for positive pressure - eg. for airbrushing, inflating tires or pressure casting you can set your manometer from 0 to +1 bar while acutally working with 2 bar. my vacuum manometer actually shows 0 to -1 increments!
@@downey2294 It's the difference between working with 'gauge' pressures and 'absolute' pressures. Gauge pressure is expressed as an offset from atmospheric pressure, absolute pressures are expressed from a baseline of "no pressure at all" and are therefore always positive. You may have seen the abbreviations PSIG and PSIA used for gauges working in pounds per square inch.
Learn more about FBFX’s work at www.fbfx.co.uk/
For anyone curious, that green tape they are using is Polyester tape, it is typically used commercially as masking tape for powder coating or other high temp masking needs and has a working temperature range of -60°F to 400°F, and is also extremely resistant to chemical attack, it can be used in most solvents, acids and bases since it uses silicone adhesive (which is why it sticks to silicone) with a chemically resistant polyester backing. It is also very strong tape, it has very high tensile strength and can also be stretched to apply incredible tension if needed. It has hundreds of uses for hundreds of tasks, for a couple examples it can be used to make very thin but strong hinges on RC aircraft wing control surfaces, it is an excellent electrical insulator even for high voltage so is useful for all sorts of electronics projects, it can be made into incredibly detailed stencils if using a knife plotter or laser cutter, it can be applied to protect fine finishes on parts as it is extremely abrasion resistant and also leaves no residue behind afterward. And that's just scratching the surface, everyone who likes making stuff or doing craft hobbies should have at least a couple rolls of it laying around, it is beyond useful. It also comes in a huge variety of widths and thicknesses, I have at least two rolls of 1/8", 1/4", 3/8", 1/2", 3/4", 1", 2", 3" and 6" widths, and several different thicknesses of 1" and 2" rolls (arguably the two most useful widths) with the thinnest being about the thickness of a sheet of paper. It's not exactly cheap stuff but a little goes a long way.
Thank you! I've been trying to find a tape for silicone for ages. Found and ordered imediatelly.
Thank you for the info on the tape. May come in handy if I ever need tape that sticks to silicone molds. I've been doing pressure casting of resin in silicone molds for over 20 years. Noted a few things about the process with this mold which they're doing in much harder ways than they need to.
Used to use this stuff in a photo lab. It would be used to attach the rolls of film to a leader card then passed through the development solution.
I was interested in what kind of tape it was until I saw it was the tape that we've been using for years. Never realized it sticks to silicone though.
I don’t even need to know about that tape and I loved that random info drop. Awesome! That’s so cool, thank you for sharing!
Wow this Moss guy REALLY knows his stuff. How great that Adam finds such super people to interview!
You can practically hear his passion for the art, and the respect he has for how these types of silicon castings were done previously! You can also see that he was pretty nervous in presenting at the first but as the filming continued, he got more and more comfortable and was able to match Adam's pace. lol
He's come a long way from drumming for Culture Club! 😂
Of course. Moss is obviously more competent than Roy. Have you tried turning it off and on again?
Great to see Adam with such a wealth of knowledge and craftsmanship appreciate the skills of someone half his age, refreshing to see
Worked nightshift in a production plastics fabrication factory in Brisbane, Australia. Vac forming signage for recognisable brands...acrylic lettering, light boxes, bullet proof money handling boxes...
Amazing amount of woodwork for a plastics factory. All the moulds...wood. Frames, wood. Outlines, wood. Mockups, wood...
Learned heaps working there...
Envy! Many of us wish we were you!
adam looked so comfortable in this envoiment, also he didn't feel the need to hold back on his knowledge with the other maker. great vid guys.
so nice to see john in a video!! I started at FBFX 5 weeks ago can't wait for your next visit!
It's always great to see how excited Adam gets as he's learning about new techniques or technology.
Two extremely professional human speaking to each other equal an awesome presentation. Thanks guys.
We need more of this in the whole planet
It's great seeing Adam so absorbed.
.. Next gen. Mr savage. Always learning and sharing.
That was really cool. I love practical effects, and I think this advance in molding helps to ensure their use.
The guy showed alot of constraint in doing the process himself and let Adam have fun.
Finally a vid I can used to explain vac casting to clients. Thanks. ❤
I've been wondering for a few years if using vacuum casting for lenses is possible/practical! I'm glad to see that it is! The process shown here is FAR more detailed than what was in my head!
Jon seems like a good dude.
Super interesting and clear, concise explanations.
Im not in to cosplay or scifi etc but im fascinated by the process of moulding.
Nice one!!
Am I the only person that thinks that if Adam decided to do a one day build that solved world peace, that not only would he do it, but he’d make a perfectly weathered box that it would fit in… he’s a national treasure!
Not that simple. He simply explains things. But, that! No
I've used that exact phrase, "national treasure," to describe him many times.
Adam is great and does a lot of cool stuff and does great teaching stuff, but he’s as human as anyone else. He has all the same biases and flaws as the rest of us.
It’s great to respect someone for their skill, experience and accomplishments, but just be careful about lifting them to super hero status.
Jesus Christ, man, calm down a little.
Ah but Adam is only human and a mistake may end up with Pandora’s box…
Crazy... Ive been watching vacuum casting vids recently. Adam is the man.
Adam: "In the old days we just used to fill a mold with some resin and sit there and [pantomimes rocking the mold]."
Jon: "Yeah, we don't do that." (dons full _Breaking Bad_ gear)
It's gotta be nice to have adam tell you 'it's been a real education"
Great video never worked with silicone like that but I have done infusion with epoxy and polyester.
This was really interesting and enjoyable to watch!
I don't know how expensive the professional silicone tape is, but I have used the bondage tape you can get in "adult fun stores" that "only sticks to itself" to tape silicone molds.
The positive side to that is, that it is reusable if you don't cut it off and try to prevent too much dust from accumulating. .
“Oh, there’s liners for your funnel! I see- Oh this is great!”
Genuine enthusiasm for something very minor. Adam’s the GOAT
This was awesome. It's so cool, and so are both of you.
I immediately had to go look up that high temp tape .. looks like it's high temp PET tape to me. Cool
Just incredible. Thank you!
Looks like the tape I used when masking off for powder coating. They use it as it's heat resistant to the 375F or so in the oven. Interesting if it also sticks to silicone.
I'm amazed Adam has not used vacuum casting before! It's been a standard in rapid prototyping for yonks.
Adam is probably well over twenty years removed from those jobs. Once Mythbusters took off, I don't think he worked in the business anymore.
"If you're not paranoid, you're not prepared" ladies and gentlemen, behold the mind of a genius
Chief’s helmet is gorgeous. Would love to have that sitting on my shelf.
Incredible craftsmanship
Laughing at the number of times Adam tries to get the info on what the green tape used on the silicone mould is.
I'd be very surprised if he left without finding it out.
looks like resin Tape (PET tape with a silicone adhesive)
@@andy-in-indy Various people call it green kapton tape, polyester high temperature masking tape, etc.
its polyester tape. Expensive af
I love how Adam uses gestures that sort of look like sign language to bridge the barrier set by the masks
18:00 At this point I needed to tell my brain: They picked the timer back up, they picked the timer back up, there is nothing to worry about. ^_^
more videos like this! good stuff
Love how Adam corrects his pronunciation for the country he's in despite not needing to.
Thought I was about to learn how to make propellars!
i would never ever manage to do that guy's job without scratching of part of the "R" on the vacuum machine.
Wish we got a closer look at how that tape mold wall was setup
Very cool. I'm taking notes!
Did anyone else get excited when they saw the Sandman mask?
9:33
What!!? Imagine.
The legend of Making says he’s your assistant. 😮😮
So what is this magic silicone tape and where is our affiliate link? 😂
3M Differential Double Coated Silicone Tape 9699? Definitely not cheap though
I was thinking it was some species of Kaptan tape. I'm probably wrong though.
I am assuming the adhesive is the secret sauce. I bought a version of this to test out. Caplugs High Temperature Masking Tape: 72 yd Long, 3.5 mil Thick, Green Polyester Film, Silicone Adhesive Mfr# SH-47520
Not Kapton, I think. The polyimide itself is what gives it that yellow/gold color.
There are other polyester film tapes with a silicone adhesive for a reasonable price, I'm wondering if that is what makes the difference. Silicone adhesives might stick to a silicone mold.
Hopefully a show and tail of the tape. I know tell.
If you’re not paranoid you’re not prepared. I’m gonna steal this quote
10:33 General good life advice, sponsored by Adam Savage's entire life.
great video. I do a lot with Smooth On. They are located close by me.
Such an awesome video!
That SO cool!
They also do this in the auto restoration field. Taillight lenses for 70 year old cars simply don't exist.
So they make them.
1. FIND a good one. If necessary, clean it up. They need to be good, but nobody is going to look through them.
2. Make the silicon mold. Much easier than here.
3. Fill mold with plastic stuff.
4. Put in tank, draw a good vacuum.
5. Pressurize the tank.
6. Wait, unmold.
I'd bet someone does this on demand. Like that place in England that makes wiring harnesses.
Wooo Go Jon!
"ADAM! WE'VE GOTTA COOK."
Now I want to Google and compare this with how they made the OG storm trooper lenses for Star Wars
Make a mold of the liner and funnel combined with clips on top to hold it in place.
The ending with Adam putting the lenses on his face and looking around reminds me of those joke scenes where a little kid wears a bra on his face in a similar fashion, not knowing what it is but pleased it somehow has that bridge for his nose that lets it fit around his face. >D
Wow super cool
A tiny human, perhaps a leprechaun, walks on the top shelf at 18:13.
I want that vacuum machine
The Padawan has something to teach the master. 👍💙😎
So next one day building is a custom vacuum gasting chamber for Adam?
@AlexanderHenry-hz3td I don´t belive in any gods because humans use them as exuse to do harm to other people and feel good about it because it´s for their god
18:14 it looks like there is a tiny human walking up on the shelf 😂
I’ve always wondered if one could forge metal in a vacuum too
You can. It's more expensive. Sometimes it's worth it. Inert gas is more common.
Yes. O'Neill's _High Frontier_ has a chapter on extracting and refining raw materials in vacuum. I'm sure the state of the art has moved on in the decades since.
Well that’s neat! I watch more blacksmithing videos than I care to admit, and see a lot of issues just because oxygen and such in the air.
@@cullumsay171Time to develop a new method and revolutionize the industry.
I myself need to make a visor voor a helmet. But i am debating if I should vacuum form it, resin cast or a completely different method. Quite a riddle to solve
Vacuum forming is the fastest and cheaper ! Just observe the transparency of most vacuum formed packagings for any consumer product.
I've been looking forward to seeing this ever since you mentioned getting back from the UK!
I love the elegant simplicity of this operation 🤌 I think you hit the nail on the head when you mentioned that this method just cuts out so much of the failure mode, of what this operation usually encounters.
wh... why are there 6 dislikes for a video like this? there's nothing to dislike about vacuum, in the most literal sense of it.
Lol looking at his PPE, I thought: Was this the inspiration for the Sandman costume?
Nice video sir
Adam loves the smell of an open flammables locker. 🤣
How is the tape attached to the model?
Silicon is also "carved" with nanometric precision in cpus and other computer components.
Silicon and silicone are very different substances.
@@robadams1645 for sure haha but they come from the same place.
Cool vid, but let's talk about the Sardaukar mask in the back.
11:08 "On today's episode of breaking bad. Our protagonist mix 'stuff' together."
how the hell do they put the tape onto the model? I mean... it must be placed on the model perpendiculary, like only with the super thin edge, right? oO
Great video!
I like that guy.
undoubtedly highly professional resin casting! i obviously am not working on your level but all that waste and extra effort (for those tiny lenses...)
and a honest question to any fellow molders, casters or physicists in general: does a soft silicone mold, fully degassed, actually expand in the vacuum chamber? (3:35) since it maintains the same density regardless of durometer and doesnt compress in the pressure pot? And dont you get a LOT of expansion by heating the mold up "as hot as possible" (10:57)? Something doesnt add up here...
Hiya, professional vacuum caster here :) in answer to your questions: no a mould will not expand in a vacuum, the silicone is a homogeneous solid material and as long as it doesn’t contain large bubbles in it remains unperturbed by the vacuum. The molds can expand slightly with temperature, to keep this to the bare minimum a 40 shore silicone as in this video is typically cured in at 40 degrees centigrade (any hotter and 3D printed masters will distort!) Most resins we use require the mould to be heated to 70 degrees centigrade before use so that the resin will properly cure. We then typically cook the mould at 70 degrees for an hour or two depending on the resin used to properly cure it. Keeping the temps consistent is the key to producing parts as dimensionally accurate as possible.
its kind of weird the paddles were activated while there still was air in the chamber. But I guess it doesn't introduce too much bubbles.
Can someone explain the mold in the oven? When I froze the vid I think the oven read 68 degrees C. Is this peculiar to the plastic they were using? Thought it odd that they did not say what plastic they were using? Does the introduction of the chamber to vacuum alter the temp of the Part A and B in the chamber?
Anyone know what the tape is that sticks to silicone? Does it come in a double sided version too?
It think that is resin tape (PET tape with a silicone adhesive). I have seen that type of tape with acrylic adhesive on one side and silicone on the other.
You can just use any old clear packing tape for taping up the molds like he does in the video. I just spent 7 hours today doing vacuum casting :)
Hey Adam, is there an injection machine for tny projects that will inject plastic into a silicone mold?
Oh! I'm sorry lol, I asked the question before I watched the video. You guys are answering my question thanks very much
Heisenberg and his assistant Adam Savage
Let them cook!
To me the tape appears to be silicone backed tape. Silicone to silicone is my guess. I would think your normal glue/adhesive tape would damage a mold.
Exactly what is the magic tape which sticks to silicone? Inquiring minds want to know...
wow
Adam, we need to cook
Was it just me or did anyone else notice Adam's watch changed within this video?
Yeh that's such a better way to mold. I remember molding small master molds with my stepdad. We had the hardest time getting a good master molds of the little houses that he made. Too be cast in plaster. But the epoxy was terrible for defects. Didn't help with so much detail. I still have his first piece that was a solid piece of plaster he carved a castle out of. I would love to mold a master from, but I dare not Incase I ruin it. Any thoughts on this would be great. Thanks for the great content. Also Adam I have a bagpipe build you may be interested in collaboration with. It's right in your wheelhouse mate. Hit me up. I'll explain the concept. Much love mate.
Maybe get the castle digital scanned then 3d print it and make a master from the 3d print?
Who thinks that some company should hire him as master prop maker, to make traditional non cgi movie effects
At 18:12, you can see the little elf climb on the shelf.
Just saying.
I saw a post on Reddit where someone put resin into a vacuum chamber to degas it and it exploded everywhere and people were saying you cannot use a vacuum chamber for resin and must use a pressure chamber instead. Is that bad advice or what is the deal with resin in vacuum chambers?
If you have too much air in the mixed resin or pull the vacuum too fast all those little air bubbles in the mix will explode outward and make a mess. But you can easily vacuum resin even with lots of mixed in bubbles, it just takes time so needs to be a slower set resin (why they are mixing in the vacuum too here - no stirring in the air if there is no air to stir in, so it won't overflow the mixing pot as all the air bubbles grow).
Helps alot if you can see through the chamber - then you can watch the rate the bubbles are making the whole thing grow and let air back in a bit and so apply the vacuum slow enough not to make a mess.
Looks like a scene right out of Breaking Bad!
Can you make bd 1
That guy sounds like Russell Howard.
Is that just Kaptan tape?
Looks like PET tape with a silicone adhesive. Several brands sell it as "resin tape" for doing things like epoxy river tables.
I think you mean Kapt*o*n (polyimide) tape, and no Kapton is a characteristic yellow colour.
How did Adam get this far with being so clumsy?
I'm 58 years old, and much more clumsy than I was at 28. To quote Indiana Jones, "It's not the years, it's the miles."
He has the extra energy to go back and fix it.
10:58 except for turning the table up and cutting the hose 😂😂 those doesn't count if you mean literally 😜
13:10
8:13 I think nobody at home wears full protection like them...
"I can see my ruby."
If you like Renishaw's vacuum kit, check out their 3D titanium printers. ua-cam.com/video/qR7V9UAa5O0/v-deo.html
I'm a bit confused. what is -1 bar mean?
0 bar is basically atmospheric pressure and if you remove that completely you get -1
@@TheZahnputz but 1 bar is atmospheric pressure right? i used to do scuba diving and i was always told 1 bar is atmospheric pressure and 0 bar would mean a prefect vacuum.
@@downey2294 huh - I should have made a quick google search before being a smartass!
@@downey2294 i think the confusion (at least mine) may orignate from using bar as a varibale for positive pressure - eg. for airbrushing, inflating tires or pressure casting you can set your manometer from 0 to +1 bar while acutally working with 2 bar. my vacuum manometer actually shows 0 to -1 increments!
@@downey2294 It's the difference between working with 'gauge' pressures and 'absolute' pressures. Gauge pressure is expressed as an offset from atmospheric pressure, absolute pressures are expressed from a baseline of "no pressure at all" and are therefore always positive. You may have seen the abbreviations PSIG and PSIA used for gauges working in pounds per square inch.
He didn't try to kiss the hot end of the pump again, did he?