# How Do I De-Bubble De Resin?



## Mark McGovern (Apr 25, 1999)

Guys,

I'm turning to you all for help with a sticky problem. I want to form a perfectly transparent pool of resin in the bottom of a clear hemispherical shell. This pool, about 9/16" in diameter, will represent the cornea in a human eye. I had to thermoform the shell (two, actually - I'm making a pair) because the eyelids of the face behind which the eyeballs will be inserted is a bit over life size. That's what has prevented me from simply buying manufactured acrylic eyes.

The problem is, I just can't seem to eliminate the tiny bubbles that get introduced into epoxy resins when the two parts are mixed. I've tried 5- and 30-minute epoxies and an epoxy urethane compound (for coating tabletops) with no luck. I even tried to seal up a coffee can with the mixed resins placed inside, then evacuating the air with my Shop Vac. Nada, zilch, nuttin'.

So I'm open to suggestions. I have considered using small (1-2 drops) of Future Acrylic Floor Polish to build up to the thickness I want. But it takes the stuff so long to dry, I have to figure that somebody on the Board will come up with something better long before the Future has set.

To quote Larry Talbot, "Aawww, won'tcha help me?" Thanks, and have a great Easter weekend! :wave:


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## lonfan (Feb 11, 2001)

Mark- Hey Bud What if you Tried "Watering Down" the Future? This Way I'm thinkin it might dry Faster for you OR hows about this I discovered by Accident that when I Primed off A Screamin' Vinyl Kit (Werewolf) I found that SOME of the Black Automotive Paint I used had remained "Sticky or Tacky So in Panic I Gave the WHOLE get a Spraying of MATTE Dull or Gloss Coat and LUCKILY it Dryed leaving the Still tacky Paint Traped Underneath! Wow It actually worked. Hope you could use this info
Happiest of Easters

LONFAN/JOHN


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## Otto69 (Jan 2, 2004)

I'd say you need to suck more . That is, sounds like you're not getting enough vacuum to cause the bubbles to expand and pop. Without a dedicated vaccum chamber and a decent pump it might be tough.


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## Dave Metzner (Jan 1, 1970)

Most resin casters place castings in a pressure chamber this does not totaly eliminate the bubbles just compresses them. 
They use a vaccum chamber to de gas RTV molds not to eliminate bubbles in resin castings.

I know that clear resins are being cast and are almost like clear styrene in appearance.

You might check into the Micro Mark catalog, I'm gonna make a guess that they have a web site where you can check the product lines thay carry.
I believe there are clear casting resins, some of these resins are water thin and can be mixed without developing lots of bubbles, I think that the thinner the resin is, the better your chances of producing bubble free castings without a pressure chamber.

Dave


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## ChrisDoll (Sep 2, 1999)

Harbor Freight has a great pressure pot for about $80. It's a paint sprayer pot.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=37515

I've used this for my pressure casting.


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## Ziz (Feb 22, 1999)

How fast or slow are you mixing and pouring the resin/epoxy? Doing it too fast will cause air bubbles. Try working a little slower, and use a popsicle stick or other spatula type apparatus to fold and layer the two compounds into each other, rather than mixing like you're scrambling an egg.


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## Otto69 (Jan 2, 2004)

*Correct me if I'm wrong..*

But is there any reason that vaccumm won't work as good or better than pressure for casting? Or does the lack of air impede hardening of the resin?

I've seen the pressure chambers at least one commercial caster uses. I'd just prefuer to use vacuum where possible since it seems less risky, and potentially more efficient in that it should theoretically eliminate bubbles rather than compress them. Of course I haven't done any casting on my own yet....


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## Mark McGovern (Apr 25, 1999)

lonfan said:


> ...when I Primed off A Screamin' Vinyl Kit (Werewolf) I found that SOME of the Black Automotive Paint I used had remained "Sticky or Tacky...LONFAN/JOHN


Lon, that Screamin' Werewolf has aways been way up on my "Gotta Have" list! You can use oil-based primers on vinyl if you apply them as mist coats. Sounds like you sprayed your black primer on a little too heavy. If you haven't finished the model yet, you could eat off the old paint with any of the removers that have been mentioned elsewhere on the Board. Wash the cleaned model with plenty of soap and water, let dry, then - HEY, wait a minute!!! You guys are supposed to be giving _me_ advice!




Otto69 said:


> ...Without a dedicated vaccum chamber and a decent pump it might be tough.


 You can say that again!




Dave Metzner said:


> ...I think that the thinner the resin is, the better your chances of producing bubble free castings without a pressure chamber.


Dave, I know that acetone will thin your average epoxies, like the 5- and 30-minute types we use on models. I've thought that it might pay to experiment to see whether the thinned resin will release the bubbles. But I am concerned about the effect the acetone may have on the resin's ability to cure, and whether it might fog the clear shell. Might be worth a try, though.




Chris Doll said:


> Harbor Freight has a great pressure pot for about $80.





Otto69 said:


> I've seen the pressure chambers at least one commercial caster uses...


I should have explained earlier that this is a one-shot project. I don't ordinarily need to make perfectly clear resin castings, so I'm looking for the simplest - and certainly cheapest - answer I can find. If I absolutely must wait while the puddles of Future cure completely, I can grudgingly do that.




Ziz said:


> ...Try working a little slower...


_Now_ you're talking - simple and cheap! Seem to me I read somewhere that somebody mixed the two parts in something like a Baggie, then squoze the clear goop out of a hole cut in the bottom. Can't hurt to try that, either.

Thanks for your suggestions so far, friends. I'll try what I can and let you know what results. And I'm still open to other ideas.


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## ChrisDoll (Sep 2, 1999)

You're not going to get the results you desire without pressure, period.


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## Mark McGovern (Apr 25, 1999)

ChrisDoll said:


> You're not going to get the results you desire without pressure, period.


But this hobby is supposed to be fun! I CAN'T *TAKE *ALL THE *PRESSURE, CHRIS!!!!*

*hoowhee...hoowhee...wheee...*

Or were you talking about the resin - ?


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## Dave Metzner (Jan 1, 1970)

Re: Vacuum and resin casting.
I'm told that resin casting is done uvnder pressure. That putting uncured resin in vacuum results in the opposite effect from the desired one - more and bigger bubbles.
I'll drop a note to Gray Headed Art - and ask his advice - he spent 10 years casting resin professionally.

Dave


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## Gray-headed Art (Aug 16, 2002)

Otto69 said:


> But is there any reason that vaccumm won't work as good or better than pressure for casting? Or does the lack of air impede hardening of the resin?
> 
> I've seen the pressure chambers at least one commercial caster uses. I'd just prefuer to use vacuum where possible since it seems less risky, and potentially more efficient in that it should theoretically eliminate bubbles rather than compress them. Of course I haven't done any casting on my own yet....


One can certainly vacuum a resin casting, however, this will more often than not lead to far more airbubbles. The problem is that unless one has a cyrogenic vacuum-system, which almost instantly creates a massive vacuum in a chamber, the slow drawing out of the air pressure by a normal vacuum pump won't get all the bubbles to burst before the resin sets up. When that happens, you don't have resin with just bubbles, you get solidified foam.

Art


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## Gray-headed Art (Aug 16, 2002)

Mark McGovern said:


> Guys,
> 
> I'm turning to you all for help with a sticky problem. I want to form a perfectly transparent pool of resin in the bottom of a clear hemispherical shell. This pool, about 9/16" in diameter, will represent the cornea in a human eye. I had to thermoform the shell (two, actually - I'm making a pair) because the eyelids of the face behind which the eyeballs will be inserted is a bit over life size. That's what has prevented me from simply buying manufactured acrylic eyes.
> 
> ...


*Mark, *

*Some thoughts here: *

*I did cast model car resin transkits and parts professionally from 1989-1999, in tan urethane, optically clear urethane, epoxy--the whole 9 yards.*

*Unless you are willing to spend some serious dollars on optically clear urethane resin, no matter what sort of resin you use to replicate the clear parts you want, you will have at least a slightly yellowish casting--there is no way around that, unfortunately. This can be alleviated by the use of color behind it, though.*

*Actually, epoxy is quite easy to "de-gas" (remove the bubbles) at ordinary atmospheric pressure. For starters, use a slow-setting clear epoxy, such as DevCon 12-hour, or the wood-surface coating epoxy you mentioned (which is either 12-hour or 24-hour cure), both will work for casting. Both of these will remain liquid well long enough (more than adequate "pot life") for any airbubbles (generated when mixing) to rise to, or at least, very near the surface of the resin. One of the hidden secrets of these kinds of epoxies is that CO2 (Carbon Dioxide) will actually "draw" airbubbles up to the surface rather quickly, and they will pop! I do this with instrument lenses on model cars every time I build a model, so I know that it works. And, you exhale a bunch of CO2 with every breath you exhale, so there's your supply--just exhale right over the top of your still-liquid casting, and you should see amazing results.*

*Also, mixing techniques have a lot to do with how much air gets mixed into the epoxy. Use, at least, those little 1-oz dram cups (medicine cups, plastic) that you can get in the RC section of most really good hobby shops (Hobby Lobby has these in most of their stores as well!) and even pharmacies. Stir the epoxy gently, but thoroughly--avoid trying to just "mix it up quickly". Then, use the exhaling technique I have described, and you will get most, if not all the air bubbles out before you even pour the stuff into your mold.*

*Should you decide to go to optically clear urethane (which is quite expensive, but absolutely crystal clear), you will need a vacuum pump capable of pulling a 29" vacuum, some sort of vacuum chamber (easily made), and then a good shop compressor and a pressure tank (to crush out bubbles formed at atmospheric pressure, it takes at least 50psi to make those disappear), capable of holding a minimum of 100psi (always think of a pressure vessel as needing 2X the pressure you are going to put in it, because if you burst one one, it hurts, and can hurt you big-time. Optically clear urethane outgasses CO2 as it cures, and bubbles form all over the inside of such a casting. Therefore, when I was casting clear (or dyed) headlight, taillight and turnsignal lenses (and I probably cast 5000 or so lenses over the years), I found that I had to de-gas the mixed clear urethane for about 10 minutes, to draw out all the CO2 that I could, then, after pouring the molds, pressurize them to at least 50psi and hold that pressure until the resin hardened. However, that was in a professional, commercial setting so it was essential.*

*Go with very slow-setting clear epoxy, I think you will do better with it, for less money, just use the materials I suggested, and the CO2 technique (oh, and stir gently when mixing) and I think you will get a good result.*

*Art*


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## Otto69 (Jan 2, 2004)

Art, thanks much for the detailed explanations. I've always been curious why pressure casting seemed more popular than vacuum casting, and now I know why!


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## Wbnemo1 (Aug 22, 1999)

Hi ,
actually you don't need to pressure cast clear resins. it is in the mixing ,never do figure 8's or full circles when mixing up clear resin, C's do the trick and pour slowly..this works useed it for years learned from a master caster, mold maker...always learning new things in this business 

William


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## Gray-headed Art (Aug 16, 2002)

Wbnemo1 said:


> Hi ,
> actually you don't need to pressure cast clear resins. it is in the mixing ,never do figure 8's or full circles when mixing up clear resin, C's do the trick and pour slowly..this works useed it for years learned from a master caster, mold maker...always learning new things in this business
> 
> William


William, 

True enough for polyester and epoxy resins. However, with clear urethanes, yes, both a vacuum chamber for degassing clear urethanes and a pressure vessel for "crushing" out gas bubbles are virtually a requirement (due to the chemical makeup of clear urethanes). In the course of what I was doing, I've had experience with just about every brand of clear urethane, true with all of them.

Art


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## Gerry-Lynn (Mar 20, 2002)

Hey - If you are using slow cure time, as well as pressure cast - A vibration would allow the "bubbles to rise.










Gerry-Lynn


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## Lee Staton (May 13, 2000)

Here are a few tricks for keeping or squeezing the bubbles out of resin:

Use a round stirrer when you mix. A flat object introduces more bubbles. I often use round plastic swizzle sticks from a liquor store.
Mix slowly, as you've been advised already.
Pour from a healthy height above where you want the resin. Pour in a thin stream; this squeezes out the air bubbles naturally. Some furniture refinishers poke a hole in the bottom of their mixing cups to squeeze out the bubbles by draining the cup in a thin stream.
One poured, you can use an airbrush with no paint to gently spray air onto the resin surface. This acts like a pressure pot and pushes down on the mixture, removing bubbles or bringing them to the surface where you can pop them with a toothpick.
I have also used vibration to release bubbles. If you have one of those sanders that vibrates, clamp it upside down on your bench and secure your item to the vibrating surface. This seems to be less successful (for me) than the other methods.
I have used a large pressure cooker hooked up to my compressor as a pressure pot. It seems less dangerous and a lot cheaper than a painter's pressure pot if you find one on sale.
Just some food for thought. I have used Decopour-type products (the ones for sealing decopage art to wooden plaques) successfully in the past to simulate water. They get far less yellow than epoxy resins.

Art has more experience and may disagree with some of my advice, but I put it out here to share.

Lee


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## razorwyre1 (Jan 28, 2004)

Lee Staton said:


> I have used a large pressure cooker hooked up to my compressor as a pressure pot. It seems less dangerous and a lot cheaper than a painter's pressure pot if you find one on sale.


yikes! sounds extremely dangerous to me........


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## Lee Staton (May 13, 2000)

It's not as dangerous as it sounds. My compressor has a holding tank with a regulator/gauge. The pressure cooker also has a gauge as well as a pressure relief valve. I carefully release just the right pressure from the holding tank by watching the pressure cooker's gauge and staying within its safe zone that's clearly marked. Believe it or not, I've found it doesn't take all that much pressure to improve castings substantially. As I said in the previous post, I don't purport to be an expert. Just sharing what I have done.

Lee


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## Gray-headed Art (Aug 16, 2002)

Lee Staton said:


> It's not as dangerous as it sounds. My compressor has a holding tank with a regulator/gauge. The pressure cooker also has a gauge as well as a pressure relief valve. I carefully release just the right pressure from the holding tank by watching the pressure cooker's gauge and staying within its safe zone that's clearly marked. Believe it or not, I've found it doesn't take all that much pressure to improve castings substantially. As I said in the previous post, I don't purport to be an expert. Just sharing what I have done.
> 
> Lee


Lee, 

One very strong caution!!!! Pressure cookers, at least those made for use at home are cast aluminum units, certainly the lids are. They aren't made to take more than about 15 or so psi, and can explode if you take one much above that--lotsa instances of that happening on the kitchen stove! Trouble with cast aluminum such as those are made of is that the castings (the lid) can fatigue and crack open easily. Back in the early days of resin-casting, there were several incidents where guys had overriden the safety valves on pressure cookers in order to get sufficient air pressure for "crushing out" airbubbles in resin, and a couple of them got hurt pretty badly.

For safety's sake, if you are gonna pressure cast, get a painter's pressure pot--lotta times, if you keep your eyes open, you can get used ones quite cheaply. Painter's pots are welded steel units, with aluminum heads that are fixed in place with 1/2" bolts at 4 points, large hand-nuts to secure them. Their lids are about 3/4" thick, far heavier than what your wife would get in a pressure cooker. They are designed to take 50psi, and are actually engineered at least 2X that, if not 3X.

And, the price of a new one is far less than a co-pay at the emergency room, IMHO.

Art


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## razorwyre1 (Jan 28, 2004)

someone posted a photo either here or over at sm of what was left of a pressure cooker after doing this stunt one too many times.... it was an eye opener.


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## Mark McGovern (Apr 25, 1999)

*Kick Me!!!*

I'll get to the why of the title for this post shortly. Meanwhile:




Dave Metzner said:


> ...I'll drop a note to Gray Headed Art - and ask his advice - he spent 10 years casting resin professionally. Dave


 Thanks Dave - that's why I started this thread, to get expert advice.




Gray-headed Art said:


> *Some thoughts here: *


 I'm not going to take up space by quoting them here. I just want to thank you for taking the time to share them, Art. Lots of good stuff there - and anyone who knows me will tell you that I can exhale CO2 with the best of 'em! 




Wbnemo 1 said:


> ...actually you don't need to pressure cast clear resins. it is in the mixing...


 That's been a common theme in people's responses, Dubbya, and I'll keep your suggestions in mind. Many thanks.

And yes, I'm talking epoxy resin here - none of that high-tech urethane stuff. Don't none of you guys get me confused with somebody who know what he's doing. :idiot:




Lee Staton said:


> Here are a few tricks for keeping or squeezing the bubbles out of resin:


 Again, I'll use just this much quote to say thanks for posting, Lee. Your advice is also helpful and very much appreciated.

You know, there's so much good, practical information floating around in cyberspace I'm beginning to wonder whether there could be a Hobby Talk book or two's worth of copy. The only editiorial work would be to sort out and organize the material. We'd need some good step-by-step photos of the various procedures, and of course a gallery of finished models. The result might be a veritable _Encyclopedia Modelica _of modeling tips and techniques.

BTW, if I can get this project finshed in time, you'll be able to view the end results at WonderFest.




Gray-headed Art said:


> One very strong caution!!!!...


 I always try to observe those, Art, but make no mistake - there are no pressure cookers in my hobby tool inventory!

Now, back to the title of this post...why do I need to be kicked (in this particular instance, that is)? A friend of mine stopped over Saturday night, and I explained my dilemma to him. "Out of the mouths of babes", as they say - or rather, drunken neighbors, came this suggestion: since the eyes are ping pong ball-sized, why not just paint up a pair to look like eyes and cut the clear domes off a couple of those squiggly doll eyes to use as corneas? He pointed out that, no matter what I do to create a pair of eyes, very little of them will be visible under the heavy eyelids of the bust in question.

So I drew an iris and pupil on a spare ping pong ball. Then from my big bag of squiggly doll eyes (in various sizes...I usually use the domes to make "glass" covers on instrument faces), I cut and sanded a quick cornea. Even with little bits of tape holding the dome in position, the effect was great!

So I have to apologize for getting everyone worked up with resin pouring issues when this simple solution was sitting there all the time. If you're in the Lizard Lounge on Friday night at WF, you can have a turn at playing "Place The Shoe Leather On Mark's Butt". I'll bring the steel-toed boots. :wave:


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## Mark McGovern (Apr 25, 1999)

Double posted - grrr...


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## Gray-headed Art (Aug 16, 2002)

razorwyre1 said:


> someone posted a photo either here or over at sm of what was left of a pressure cooker after doing this stunt one too many times.... it was an eye opener.


Or, and eye eliminator! Please folks, there are some things you DO not want to try at home!

Art


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## Lee Staton (May 13, 2000)

And thanks for your advice to me, Art. It is appreciated! As I said, I always *very* carefully stayed in the safe zone of the pressure cooker's gauge. But I don't cast anything these days and don't intend to. I'm trying to restrict my harmful chemical exposure to well-vented acrylic paints. I've had too many friends in the movie effects business develop lymphomas to think these activities are as safe as we all think they are just because we can do them at home!

Lee


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## Dr. Syn (May 29, 2003)

I don't know if this will work for what you want but Woodland Scenics makes a product for water. You pour it out in thin layers and it dries clear with no bubbles. I get it at train shops for about $15 a bottle. Might work for you.


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## Mark McGovern (Apr 25, 1999)

Thanks, doc. I was playing with the idea of using that - in fact, I was chastising by buddy about having borrowed my bottle of Water Effects and not returned it yet when he suggested the idea of creating the corneas from the doll eye domes.


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