Which One To Use, When, How? WHY IS THIS SO HARD? !!!
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- Опубликовано: 21 апр 2022
- 1: Use vacuum to de-air the silicone rubber before pouring the mold.
2: Use pressure to prevent bubbles from forming when pouring resin into the mold.
The End.
Now you don't have to watch the video!
Thanks to the following companies for supplying the materials used in this video:
Freeman Manufacturing and Supply
www.Freemanwax.com
Silpak
www.silpak.com
Here is a list of suppliers for many of the materials I use in my videos:
www.dropbox.com/s/kz6mhmf7v5v...
Do you have a project to suggest for the channel?
Here’s a .pdf with everything you need to know:
www.dropbox.com/s/pjb0l6fr7zj...
Reach me at roberttolone@yahoo.com 
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Not only is this highly informative as always, I just love listening to you explain. You're the Bob Ross of casting 😄 If they do audiobooks on manuals then the job should be yours!!
Hear, hear!
Thank you very much Mr Talone, I’m a college student who is now graduating from my CNC manufacturing course but before I could I needed to complete a project that involved silicone molding and resin casting. Typically I deal with metals and machining so it was a big switch. No one else on RUclips has more informative and well put videos about the process. This seriously was one of my greatest helps so thank you for indirectly helping me graduate 👨🎓
I have learned far more by watching your videos, than anyone else in regards to casting and mold making. I as always appreciate your wealth of knowledge and your willingness to share.
Got a pressure pot because of your videos! Thank you VERY much for all the great advice!
Both pressure casting and Vacuum casting use the same idea. All the vacuum is doing is expanding air in the mold so most of it finds its way out. Once full vacuum is achieved, you STILL have air pockets in the mold, its just the air is at nearly zero pressure. You then Release the vacuum while the resin is STILL liquid and before it has gelled. Which is slamming 14 lbs per square inch of pressure on the resin, compressing any remaining air into bubbles so tiny they are microscopic. Casting under pressure is just slamming the high pressure on the resin with the air in there still at 14 lb/sqin… so the critical difference comes down to TIME. With vacuum casting you need to be able to evacuate the chamber, and release the vacuum before the resin gels or sets. With pressure casting you want the resin to gel or set UNDER PRESSURE before you release the pressure. SO generally, we pressure cast with urethanes. We vacuum cast with polyesters as we have a lot longer time for polyester to gel. But if you don’t have a fancy pressure or vacuum system, you can still get good casting by designing a mold with proper venting, so the incoming resin can push air ahead of it and up out the mold. And if you dust the interior of the mold with talcum powder. Just a fine trace of it. This prevents surface tension in the resin from holding bubbles against the surface of the mold and allows them to either rise out thru venting, or with a little swirl of the filled mold, to migrate away form the surface of the casting.
Man this video is amazing. I’ve had that exact question of why not cure while in the pot. Great great explanation!
Glad it was helpful Uncle Jessy!
Great video! Even though the principle is simple, I can understand why people get confused.
The main question I've been getting is: do I really need to get a vacuum chamber? Can't I just use a pressure pot? Or, do I need a pressure pot if I already have a vacuum chamber?
My answer is always, if you are going to use a vacuum chamber, you won't see much difference unless you also use a pressure pot.
And if you use a pressure pot, you will have bad results without using a vacuum chamber.
The former is because a pin-bubble free silicon mold won't help you get rid of the resin bubbles.
And the latter because a pressure pot will push the resin into the pin bubbles on the surface of the un-vacuumed mold, giving you a rough surface.
Either way if you get one, you need the other.
You may have seen my comment from a previous video( my time line, not as posted) great job. I've learned a lot from continually watching and filling in my own gaps then I expected.
3:28 on the Time-Line is not just the Quote-of-the-Week; but, likely the Quote-of-the-Year!!! LOL!!!! And, the delivery was so cool and nonchalant LOL!!! Robert makes Friday the best day of the week!
So which is better sucking the mold dry or the blow job on the mold?
Something I do for "sealing" my resin containers is to put a gasket on the container and then tighten the lid on it. I just cut a chunk of plastic bag for the gasket. (Use PP bags) It works pretty well to keep the build-up of resin out of the container threads.
I put a tiny smear of vaseline on the threads of my jug of wood glue to prevent the cap from getting glued on.
But of course, with these delicate chemicals and our concern for their purity....that would be a technique I would apply with some discretion.
Thank you Robert, excellent video, I love it.
I’ve never made a casting, but watching your videos makes me happy! See you next week!
It remembers me what happened to a friend that worked for a tiny models company. They didn't use RTV rubber, instead they used one that has to be vulcanized with heat and pressure. And that was kinda fine while they used for green stuff models. They received a model made in different materials (included fimo). When they pressurized it they crushed completely the wings, and body had to be partially reconstructed from the first (faulty) cast that then served as master. Also other models tiny scale vulcanized under pressure looked skinner and with squished details.
Thanks for your video well enjoyed 👍. I gave it two thumbs up
Ohhhh I been looking forward for this!
Fantastic! Thank you.
You never fail to make this Granny chortle! You are adorable Mr. Tolone, I always learn new things with you Thank You. Stay Groovy✌~N~💖
I came here for the tips, I stayed for the science
Man, you rock! Thank you for sharing such a rich knowledge. Cheers, from Brazil.
Good to see a thorough video! A recent video by Squidmar had them struggle casting resin and letting it cure inside the vacuum - the model kept exploding and I think they tried it over and over more than 30 tries before it was acceptable.
Weird. I thought this came into my feed because I like Pask Makes, but maybe it was Squidmar that got me here. Either way, it’s good stuff.
For anyone who is interested in the science of polyurethanes and why they foam read on and I will explain.
First a bit of background on what polyurethanes are made from, you have two liquid parts which when mixed react together to form a solid this reaction is non-reversible. The two components are a polyol (I would refer to this as the base or resin side) and an isocyanate (I would call this the hardener). Polyols are characterised by terminating in a hydroxyl group (-OH) and to be useful for this application they need to have at least 2 hydroxyl groups per molecule. Isocyanates are characterised by an isocyanate group (-NCO) and once again you need 2 or more per molecule to be useful in this application. The R-OH and R'-NCO groups react together to form a urethane linkage R'-N(-H)-C(=O)-O-R (where R and R' are the rest of the molecules).
Now when you add water to the mix (H-O-H) you have a hydroxyl group which can react with an isocyanate unfortunately it doesnt result in a urethane linkage you get R'-N(-H)-C(=O)-O-H but that nitrogen in the middle would be much happier if it had another hydrogen friend so it steals the one from the end and you end up with R'-N-H2 + CO2 this gives us our bubbles, but isn't the end of the story the R'-N-H2 then reacts with a R'-NCO to form a urea linkage so while you get a different product it still cures (as long as you have sufficient isocyanate).
So you get carbon dioxide bubbles being formed and this is used to good effect in polyurethane foams however, not what we normally want from our casting resins. The problem of moisture contamination is then twofold first it makes bubbles in your casting (which can be mitigated by application of pressure as Robert has shown) secondly it pushes off your mix ratio, every water molecule is using up 2 isocyanate groups which should be reacting with your polyol. In most cases the resin will still cure to a solid but even if the bubbles are suppressed the end result may not have the physical properties the resin should have achieved (hardness, flexability, strength, etc.).
Hopefully that makes some sort of sense if anyone has any questions feel free to ask.
Hey Chris, thanks for this explanation!
This is awesome, thanks! What little materials background I have is all solid state physics but I’ve been learning a lot about polymers for the last few months.
“I just got this bucket, cut out plexiglass, routed out a lid…. 😂🤣😂🤣” OMG! Glad you have the skills and understanding to DO that! How do we common folk make one? Or know which one to buy?
Nowadays you can buy vacuum systems online that are pretty reasonable and work well. Make sure the manufacturer says it’s suitable for casting resin.
Thank you Mr. Robert, that was very informative.
Hi Robert, thank you for the great video. I’ve been looking at pressure casting my silicone moulds and you’ve saved me from destroying my sculptures!
I have the same Amazon vacuum system. I just use a bicycle pump for my pressure pot action figures. What a bit of modding for the bicycle pump to work for your pressure pot. It works for me. Absolutely no air bubbles in my resin.. Great video great tips!.👏👏😻👍
How big is your pressure pot and how long does it take to bring it up to pressure?
@@RobertTolone Tell me what you think about this idea:
3.5'x chamber made of plexiglass and blowing air using high pressure pump w/ strong valve.
I see no reason why it would not hold up well using steel brackets, bolts, nuts, screws and a high-pressure hose. My pouring always includes a powdered metal with it such as aluminum / bronze etc.
This was a great video, as always.
When putting resin in a vacuum chamber, some components start to evaporate. This can change the composition and have a negative effect on the part properties.
At times when we have to degas epoxy for technical reasons, we keep the time in vacuum as short as possible.
Please keep those videos coming.
Guess what... Another amazing and simple explanation.
Learned so much from this channel.
Would love to see the sculpture in pressure and vacuum. Hopefully some day an example vid will happen. Thanks
I admit that I was reluctant to spend the time to make a clean sculpture only to destroy it for demonstration purposes. If you’re willing to volunteer to make a nice smooth model built on an armature full of air I will be happy to crush it for you under pressure! Just keep it small enough to fit into my tanks. Oh, and pay for the rubber! It would make a nice video demonstration.
Man, you do good work 👏 Thank you.
That’s Robert!
Great video as always Rob. I'd made a similar error in the past making a mold of an old bionicle mask. I wanted to make sure there were absolutely no bubbles left after pouring the silicone, so popped it back in the vacuum chamber after the pour. Despite being a completely solid piece, air escaped from under the wax pour spout I'd added to the mask, dislodging the whole piece and reintroducing bubbles. Even when molding a solid piece this can still be an issue if you're not careful.
Never once have I been bored by any of your videos Robert. While I'm yet to get into casting myself, I can only assume that as a result of your tutelage I'll get it right every single time without a single failure or bubble or imperfection... I'm glad you agree!
Nicely done. I wish I was shown these examples before I learning this the hard way. Those two vacuum pumps, what glory. You could crush a rail tanker with those.
Loved the video as usual 👍
Great video Robert! I have a sudden urge to rewatch Spaceballs now for some reason haha. Who else heard that reference?
This guys awesome! So fun to listen to.
Great job, Robert!
I recently did a big experimental project with new rubber and mold cases made from pink extruded polystyrene (XPS) foam, and threw the molds in my pressure pot. The failure was spectacular! When I added 40 PSI to that pressure pot, the mold collapsed and I came back to a pressure pot filled with escaped rubber! This video should help anyone avoid that same mistake.
Many a poor fool (like myself) has put things made of foam in a pressure pot. It’s not a pretty sight!
Hey! I have that vacuum pump and pot at home! I haven't used it properly yet I stopped short from buying silicone and resin to cast. I reckon why not, I was worried about the pressure pot exploding but I think it's probably relatively safe.
Another great explanation!
I believe it's also recommended to only pressure cast a mold only if the mold was created with vacuumed silicone.
Also, a can of dry air can be sprayed into your resin bottles prior to closing to help reduce moisture in all the empty space in the bottles.
What you believe has little bearing on reality.
Your video came RIGHT on time. I just got a CA Air tools Pressure pot and this has been my first week trying it. I am absolutley BLOWN AWAY by the difference of not having one. I was close to giving up on this hobby, but I got a quiet CA Compressor and the pot from them, and I am just shocked with the ease of use. I'm in the money hole, but I feel like in the LONG RUN, this is going to be SO WORTH IT. THANK YOU-- Honestly some of your previous videos really convinced me to pull the trigger on this.
I'm mid-way through the video now So I'm excited to hear what more you have to say!! Your videos have been quite literally the most VALUABLE, CASUALLY PRESENTED advice on the entire internet. Some of the vids on casting are just so technical or more so specifically on dice casting and mold making, your videos and your past in toymaking has extremely EXTREMELY helped me get through some tough spots when it comes to making stuff. I pulled my very first toys I made from scratch/ my own 3D prints (Pressurized my silicone for the first time as well!) They came out and I almost cried ahaha. No bubbles, and I had tested one with mica powder.. looked professional. GAH OK Enough ranting, I'm learning so much from this vid alone.. even though I got a Pressure Pot I was still confused on if I needed a vacuum.. but you laid out out perfect... One SUCKS.. other one BLOWS. Got it! 😂
Great information-thank you.
Great info there Bob . Hope all is well .
Good point Robert on model construction and pressuring molds. This can cause some real surprises when you open the mold and find not only a failed mold, but a destroyed master if you (high) pressure the wrong item (eg weak masters w voids, glass objects etc).. Can come out resembling the end results of a transporter malfunction.
We make our own masters and can control that aspect. I’m happy we don’t have to deal (much) with other folks masters! We pressure our molds at 10psi over what we’ll use for when we pressure the casting. Why? We’ve found that this helps prevent mold blowouts, eg BBs on the casting and essentially a ruined mold after it was pressured. We’ve got a vacuum system, that rarely, but on odd cases gets used. As mentioned in my previous comments (I think on this channel) we are in DFW area and temp/humidity is a big enemy. So we do all our molding/casting & mold storage in a temp/humidity controlled environment; gives us year round consistency. We pressure molds and castings because for us, it streamlines our workflow. We’ve arrived at this over the last couple of decades by a lot of trial and error, talking w Reynolds(Smooth-on) [our local store has many decades+ years combined experience] and other model resin kit casters (one who did large (1/350) scale model ship model casting in shop made aluminum $$$ forms!) most of whom sadly are no longer with us. If you want to see an example of BBs don’t vacuum or pressure your mold..but do pressure it while doing your casting (we mostly use 55psi, make sure your pot is safe for this and any other pressures your using, we started w homemade converted pots but now use commercially purchased purpose-designed pots): warning afterwards, the mold and casting are likely throwaways. Note: for molds which we don’t pressure set, that mold is always clearly marked/coded so we don’t accidentally grab it off the shelf and toss it in the pot. Yeah, been there done that 🤦🏻♂️.
This is what we found works for our needs, every reader’s situation is likely different, don’t be afraid to experiment, it’s part of the fun and the challenge!! 🤙
As always, just sharing, nothing more. nothing less.
Thanks for your detailed comment. I pressure always cure my resin castings in rubber molds that were cured at normal room pressure. You don’t have to cure a mold under pressure to cast with it under pressure. It works just fine.
@@RobertTolone one grey hair to another, that one we’ll likely have to agree to disagree on Robert at least for now. Unvaccumed or non-pressure cured molds, we get BBs 90% when pressure casting. We primarily use Mold Star 30 & 20T and some Mold Max 40. Long long ago used silicons (tin) from Bragdon (decades ago)with same BB results. I used to do demos at local Modeling meetups (Eaglequest etc) and would show the BB example. It’s fantastic if you get different results through your process with those same materials, I’m all ears would like to see where we differ and see if I can eliminate the BBs without having to pressure/vacuum the molds before pressuring the casting 😀
Excellent advice from the master!!! THANKS!!!
Dude, you are the best. I'm just in the learning stages of casting - and I find you vids super informative AND entertaining with your pithy explanations and no nonsense. Trust the experienced craftsman always! 👍🏼👍🏼👍🏼
Thanks for another wonderful video. It explains everything well and I love your type of attitude and humor during these videos, keep up the great work!
It seems so obvious once you've done it a while, but I remember being confused about all this when I first got into it and before I started watching your videos. I recommend your channel to anyone interested in this craft but are having trouble understanding various materials and methods. Thanks for sharing your time and expertise.
Thanks Matt!
this video was asmr for me. Really love how your built your cover :)
Thank you for that
The man, the myth, the absolute legend
really informative! sorted all my curiosity
loved it
Informative and entertaining as always.
Thanks for this vid!!
We love it!
Thanks for this
The thing I see a lot from amateur mold making videos is people using a pressure pot when they poured rubber on the master to get the bubbles out (they put the master with the rubber into the pressure pot to cure), it seems to work but from what i understand of the pressure pot is its not actually removing the bubbles and just shrinking them, in this case would the bubbles in the mold distort it outside the pressure pot and the bubbles return to they're original size (assuming the silicone is soft enough)? same as the reason you would want to make sure to vacuum the silicone of any molds would would later go in to a pressure pot?
thank you for this, it was really useful
Nice one, that was very interesting to see.
I always use vacuum for my rubber and pressure for my resin because I learned that from your videos.
But it was very very nice to see in this video, why I do it. :D
Analytics tells me that fewer of my regular viewers watched this video. Thanks for watching Roger!
Vacuum is low pressure, meaning the air inside the mould/resin will expand and coalesce into larger bubbles that will rise to the top quicker. The pressure pot increases pressure and has the opposite effect in compressing the bubbles down until they're so small as to not being at all noticeable, allowing the resin to cure bubble-less.
Bob, this was a great video!! You should number it “1”!!! A must for anyone that does MOLDS & RESIN. A MUST SEE VIDEO! I have a question for you that needs to be answered: when do you use TIN SILICONE & when do you PLATINUM SILICONE? Thank you. Richard
Great idea for a video! So good in fact I’m working on that subject right now! Great minds think alike.
@@RobertTolone I believe that we do think alike. Glad to hear that you’re working on the video. I can’t wait to see it. Best regards, Richard
Once again Robert you never cease to teach me something. One question, what is the PSI you pressuring the resin at ?
From my experience some resins actually set almost immediately if you use too much vacuum. I think one of the components has a stabiliser which stops the resin from setting until the catalyst part is mixed in. The catalyst actually binds to the stabiliser allowing the rein to set. The vacuum can evaporate the stabiliser causing the resin to set within seconds.
I have never experienced that because I almost never vac resins. And my resins set up so fast that if I do apply vacuum it’s only for a few seconds. But it’s interesting that you have seen vacuum do that to resin. One more thing to look out for.
7:27 - so understated: especially with ubiquitous Smooth On sample size containers. The lids have a much greater radius and even with my best efforts to clean them before putting them back on, I keep a small pipe wrench to ensure I can open them again.
10:23 - YES! California Air Tools compressor! They are light and QUIET! So if you live in an apartment, you won’t disturb your neighbors performing your hobbies at night. Just be careful of TWO things: 1) when you first get one, check the air tank to make sure there aren’t any metal debris from the manufacturing process (shake it to hear any rattling about)2) Be VERY careful installing the muffler. It’s made of cheap plastic and the directions are horrible at telling you were to install it- one torque too tight and it can easily break. (The muffler goes in the back as your facing the front of the compressor- on the compressor assembly itself)
Thanks Robert for another super informative video!
Great advice about the California air compressor. I love mine for how silent it is.
I thought your vacuum pump sounded familiar! I have a similar Welch vacuum pump. I only have it because it was a very good deal on Craigslist. It's overkill for me at the moment, but I expect to utilize it more in the future.
Great video as always!
I could afford only one thing and went with pressure pot. That changed everything for me, and there is no going back now. But when you put casting into pressure put using rubber that wasn't de-aired, you are going to have a bad time, haha. So many pimples on the casting. Since I can't afford vacuum now, I use pressure to make rubber "de-aired". I cast my own designs, so I knew the sculpture and never crushed it with pressure. Only once I tried to make a mold of a small decorative pumpkin, but it was made from foam so... At least it was small.
Pressure curing rubber works fine as long as you are certain that you won’t damage the model.
this video is quite obvious and understandable. the real debate is between 3d printing over the traditional means, what is the benefits of one or the other, at least if you are invested in sculpting in digital or physical and want to be able to reproduce your work.
I love 3D printing and have no doubt it will become the mainstream method for making objects. But I do believe there will always be old-school hand sculptors who need to cast their works in resin, bronze or other materials.
Loved this! Answered some of my most burning questions re molding and casting. Wondering if you have links to those pumps you showed at the end? Also isnt there a minimum or maximum pressure to look out for?
Look for a vacuum system that the manufacturer says will de-air resin. I run my pressure pots at 50 to 80 psi
Is it safe to use a vac chamber pot in a normal room if Im only using it for silicone rubbers?
Im kind of curious what a vacuum or pressure pod would do to plaster in a silicon mold?
Your channel is fantastic at covering all things casting. But would it be possible for you to do a video discussing how you price jobs? I would be interested to hear your thoughts on how complexity, casting method, materials cost, time, etc. figure into your job estimates. Thanks!
Thank You. That's exactly what I hoped you personally would suggest. I believe I have found a few "perfect" vessels, it's 12-13 feet long, but only 6-8 feet once I get the ends squared, with a 44inch interior circumference (pre-cleaning/resurfacing) and an average exterior circumference of 55ish (also pre-lathe) leaving more then enough to cut down to at least two tanks , they'll cut the ends off and turn it inside and out but I got to turn the tube(s) into tanks ie. have bottoms welded on find some way to NOT make the pressure chamber a bomb
You will need a very high volume compressor to bring those giant tanks up to pressure before your resin cures.
@@RobertTolone My plan is to make two tanks out of the tube, with the largest one 3ish feet tall (though I doubt I'll need that much height). What's terrifying me is the lid for the pressure pot. Until I meet someone with the necessary engineering experience I'll just have to get a "ready-made" one. But as to your statement even the taller tank will still only have a (estimation) 6-7 cubic foot volume and that's the one I was planning to be the vacuum chamber. Is that unusually large?
@@RobertTolone Circumference not Diameter. Wow yeah that would be Huge, My bad
Interesting
Is there any reason why I can't use the same pot for vacuum and pressure? I've got an El Cheapo pot from harbor freight. Works fine for pressure. Can I just buy a vacuum pump and appropriate fittings? I guess I could add a plexiglass top, if I want to see what's going on.
Hi Robert do you have a diagram for the vacuum chamber you made ?
Thanks Robert, great video, as ever. I found you through the Crafsman.
I'm struggling to get my pressure pot above 30psi as it's originally setup as a paint sprayer and there's a spring safety valve on there that pops when I go much over that.
The pot is rated for 50psi but if I can avoid messing with safety valves I definitely will.
My question is - will 30psi do the job if I have a slow cure resin?
Thanks so much for your time.
I run my pots around 50 psi so I don’t really know ho low you can go and still get good results. Experiment until you get a good result. Make sure your mold cavities are properly vented.
just wanted to point out that from 1:10 to 1:20 the vacuum sound doesnt let us hear you. i guess that can be fixed in edit
Oh great now i have to buy a pressure pot
OMG WoW thank you dear !! I was just about to buy a vacuum machine for my resin art... haha.. much LoVe!!!
Are you already using a heat gun? That works very well to remove the bubbles as they rise from clear epoxy resins.
@@RobertTolone yes thank you for your reply 💙 heatgun works most of the time, but not with my wing molds.. These always catch bubble HOLES to all sides.. And I want to craft many of them for my crowns for the upcoming shop.. So I am looking for a propper solution.. Especially when buying more expensive resins.. Could you actually recommend me a very clear heat and impact resistant resin (for 4mm thickness) that's less expensive than crystal clear from smooth on 💫🙏💫
great video, you have helped me no end. only question is what is the minimum presure you need for resin. my pot only goes to 55psi
I run my pots at 50.
very entertaining
Does the client go in the vacuum chamber or the pressure pot?
Is there a good vacuum pump with no oil fumes ?
you showed the home vacuum pot but, what does the pressure pot look like for the home user and where would I get one....I saw the compressor but, what about the pot?????
On slower curing resins, is a vacuum ok to use before pouring? I am very new to this and just trying to learn. And how much pressure in your pressure pot?
Thank you for your informative and inspiring videos! I'm a new subscriber and your mold making videos caught my attention. I am casting with Cementall. It is a brand of quick set cement. Do you know if a pressure pot would work with that material? Thanks again!
Are you getting a lot of bubbles in your castings now?
@@RobertTolone not a lot of bubbles. I tap the mold quite a bit, but I still get some. I’m not even sure a pressure pot can be used with cement.
Have you experimented with using something like Bloxygen (or if you have an argon tank in your welding setup) in the resin bottles before sealing? I've been told it works wonders keeping paint in a can nice and fresh. I reckon it might work with epoxy too?
I did a video on the subject: ruclips.net/video/FBC9xQ6H4oc/видео.html
the only problem I see is that I don't use fast cast resin, mine sets up in like an hour so would a vacuum chamber be better than a pressure pot? or the same?
Love the science portion. It would be great to show the science of why you don't want to vacuum silicone with your model in it. Maybe mold a ping-pong ball under vacuum with a small hole for the air to escape? Could use clear silicone too so we can see what's happening.
Good idea to demonstrate that with a ping-pong ball. That’s an experiment I could do on the channel.
If you don't have an air compressor, could you get by with a bicycle/manual car tyre pump, or is the required pressure for casting too high?
No, a bike pump can reach the necessary pressure. The problem is how long it will take you to pump up the tank. Bike tires are actually a very small volume of air. But you could pump up a storage tank until you have a sufficient volume of air at high pressure. Then release the air into pressure pot. I think after a few castings your arms and back would be really sore! But it could work if you are making small parts and your pressure pot is really small. If nothing else you’ll get a great workout!
Would vacuuming slower curing resin be acceptable? Lets say you vacuum the bubbles out and then pour it into the mold? Thank you for your videos, Im looking to cast my first resin sculptures based on my 3d prints soon.
Possibly, if your resin cures slowly enough. For urethane, vacuuming wont solve the foaming problem. For epoxy, I have found that warming the resin with a heat gun removes bubbles more effectively than vacuuming.
Great job, Robert. Thanks. Regarding evacuating resin, the bad outcome in your example seems related to the relatively short cure time of the resin you used. I have some clear resin that takes 24 hours to cure. Would there be any problem evacuating it for, say, 15 minutes, before pouring?
Also, if you're using a model known to be solid, is there any reason not to pour in the rubber haphazardly and then evacuate, followed by some time in a pressure pot?
I also cast in epoxy resin with a 40-60 minute working time, with my current work I pour into my moulds, then vacuum & leave it for 20-30 minutes before letting it return to almost atmospheric pressure (mainly just for security, my kitten can't knock the lid off if it's held in place) until cured
If you are certain that your model can withstand vacuum and pressure you can do it. Of course your mold case has to be big enough to contain the expanded rubber while it degases.
What about vacuuming the A&B separately before mixing? I know you’d still introduce air bubbles while mixing, but is there any added bubble reduction in the final cast? With and without pressure?
The foaming in resin is a chemical reaction that begins when you mix the A and B sides. So vacuuming the resin before mixing doesn’t help prevent foaming.
The explaining of "why dont you put your piece into the pot with the rubber" part left me with a question... you talk about clay models and such, but casting is not always about clay, is it? I mean what if I want to replicate and old plastic part, or a 3D print or make it a bit stupid... a steel bolt?! Theres no way of crushing that... so would it make it a different scenario?
Thanks!
I think some of the confusion about vacuuming resin is I believe some epoxy resins are vacuumed. I think in epoxy floor coating you vacuum the slow curing resin to remove any bubbles since a building sized pressure vessel is a bit of a challenge. 😸
As I have posted before I have vacuum system that uses that still small pump but use small Mason jars with a custom lid. The stuff I vacuum is under vacuum for hours or days so that kind of lid system maybe not be able to handle it.
My pressure vessel is a converted Harbor Freight paint pot. But if you want an off the shelf one California Air tools sells one already with the correct setup.
It’s true that you can set slow-curing resins like epoxies under a vacuum. But for clear epoxy that I pour out onto surfaces it’s much more effective to use a heat gun.
Excellent video as usual Robert. Just one question. How much pressure is necessary in the pressure pot?
I don’t have a scientific answer, meaning that I haven’t tested a wide range of pressures. My tanks can be pressurized to 125 psi but I usually run them at about 50. I used to run them at 80 but gradually lowered it because I got the same result at the lower pressure.
@@RobertTolone Thanks. I can do up to 60psi with my smaller compressor so that’s good.
Whats an affordable pressure pot?
Robert, do you ever cast in self skinning foam? I wonder how that differs from casting in resin.
It is a foam so you must have a mold that can withstand the pressure of the expanding foam. Also I believe you must use effective release agents as most foams are very strong adhesives.
@@RobertTolone That's the part that was always missing in the Face Off TV Series and it was driving me nuts. They never showed a foam cast, only the before and after. The only info I have been able to gather is that the mold is usually made from hard gypsum plaster like Ultracal 30 and that they're using a huge syringe to inject the foam mix in the mold. I'd really like to know more about the technique but it seems to be a prized knowledge that rarely gets out of the FX shops...
Love it.
Though, it's obvious why you wouldn't vacuum a quick cast resin, but what are your thoughts about something slow setting, like epoxy? I've avoided doing this because I've seen people try, and it made a huge mess. That aside, what do you think?
I have found that it is easier and faster to take the bubbles out of epoxy resin by pouring it into a shallow pan and using a heat gun to warm the epoxy. This causes the resin to clear very rapidly. Much more effective than the vacuum chamber. That does not work with urethane resins however.
I've worked with fast cure and epoxy resins for 4 years. If you have a pressure pot, there is no need to vacume anything. Theres no need to try and do any tricks to remove bubbles either outside maybe taking a lighter to the top of a mold to pop any colected surface bubbles. Even for making the molds, I've only ever used a pressure pot, just casting the silicone at 5 psi higher when making them then what I will the resin going into the finished molds. People have this weird idea that you have to go through hoops to make sure the resin is clear before pouring, but a pressure pot removes all of that. Shrinking down small bubbles to the point of non-existances and forcing bigger ones to the top where they pop.