# bubbles in alumilite



## HuntsvilleTurner (Oct 14, 2018)

Good day Gents,

I'm new to casting and trying to figure out 2 problems in particular:

1) I end up with very small bubbles in the upper 1/2 of a pen blank sized casting with Alumilite Clear. I'm using a pressure pot with 50-55 PSI for 45-60 minutes and still getting this wonderful phenomena. Any thoughts on how I might be able to clear them out in future castings? They show badly in translucent castings as well as in fully colored castings after using a plastic polish compound. (see photo)

2) When using a silicone mold to cast pen blanks with Alumilite Clear, the corners of the resin looked to be "sucked down". This doesn't happen in a corrugated plastic mold, on on the silicone. I can get a picture of this if needed.

TIA!


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## Tony (Oct 14, 2018)

@rocky1


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## rocky1 (Oct 14, 2018)

Pure resin, or are casting something in the resin? Typically an indication of moisture in whatever you're casting, although Alumilite does create bubbles in the curing process, and not getting things mixed precisely can cause this issue as well. Temperature may be affecting the cure causing it also. 

I have a terrible time with Alumilite down here in Florida, between the humidity and temperature. Extremely aggravatin!

Reactions: Thank You! 1


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## rocky1 (Oct 14, 2018)

Oh yes... On the second issue, I would guess that caused by the action of the alumilite curing, drawing material away from the corners as they cure. If you cure a batch of alumilite on your bench, and watch it cure with pearl in it, you can see the resin the rolling over as the resin and pearl moves. Did some knife blanks for Neil Yeag that exhibited rings in the pearl where it was rolling in the mold. Had no clue what caused it until I was working a batch that started curing on the bench. It's cool to watch, but you'll find lots of bubbles in it afterward. 

Have seen dips in the corners on my molds, but those are home made cutting board, I gorilla tape them together, and occasionally I get a little seepage around the joints. On a silicone mold you shouldn't see that, so I'd blame it on the curing process.

Reactions: Thank You! 1


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## HuntsvilleTurner (Oct 14, 2018)

rocky1 said:


> Pure resin, or are casting something in the resin? Typically an indication of moisture in whatever you're casting, although Alumilite does create bubbles in the curing process, and not getting things mixed precisely can cause this issue as well. Temperature may be affecting the cure causing it also.
> 
> I have a terrible time with Alumilite down here in Florida, between the humidity and temperature. Extremely aggravatin!



Well maybe I'll just have to check on the humidity coming from my compressor. It's just wierd that it's at the same height in each blank and that it doesn't go away with the right pressure and time. Makes sense that it could be humidity. Thanks!


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## rocky1 (Oct 14, 2018)

It is aggravating I KNOW, believe me I KNOW!! Every time I pour anything it seems I learn a new lesson in what can go wrong pouring resins. I think Tony tags me because I have the most experience in problems with the stuff. 

How warm is your resin when you pour it Bradley? If you're storing it in the refrigerator, you may need to warm it some before pouring it. Especially holds true on small pours, the resin doesn't generate enough heat to cure properly if it's to cold on a small pour. I believe the alumilite instructions say to warm it to 155 degrees, but I honestly don't think I'd go that far. Sitting it out in the sun for an hour or two down here in sunny Florida seems to make any resin work much nicer. By the same respect however, that makes them all cure faster, so you have less time to pour it, get it in the pot, get latches screwed down, and get it under pressure after you mix it. 

Another thing a lot of the alumilite pros do is weigh their resin, rather than measure by volume. Not sure which way you're going there, I was mixing by volume using automotive paint measuring cups. I've tried playing with it to see how far you can go to slow it down and give it more time to adhere to my blanks while it set, and alumilite is not friendly in that respect at all. It doesn't take much deviation from 50/50 and it simply doesn't set. There is no adding additional catalyst to it after the fact either, if it doesn't set your screwed. Clean your molds and start anew. 

The quicker it cures, the more stable your colors will be. But, there is a very fine line between setting to quick and not quick enough. With no climate control in my shop, and high humidity here in the sunny south, my window for perfect pours is extremely limited unless the weather cooperates fully.

Reactions: Like 1 | Informative 3


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## HuntsvilleTurner (Oct 15, 2018)

rocky1 said:


> How warm is your resin when you pour it Bradley? If you're storing it in the refrigerator, you may need to warm it some before pouring it. Especially holds true on small pours, the resin doesn't generate enough heat to cure properly if it's to cold on a small pour. I believe the alumilite instructions say to warm it to 155 degrees, but I honestly don't think I'd go that far. Sitting it out in the sun for an hour or two down here in sunny Florida seems to make any resin work much nicer. By the same respect however, that makes them all cure faster, so you have less time to pour it, get it in the pot, get latches screwed down, and get it under pressure after you mix it.
> 
> Another thing a lot of the alumilite pros do is weigh their resin, rather than measure by volume. Not sure which way you're going there, I was mixing by volume using automotive paint measuring cups. I've tried playing with it to see how far you can go to slow it down and give it more time to adhere to my blanks while it set, and alumilite is not friendly in that respect at all. It doesn't take much deviation from 50/50 and it simply doesn't set. There is no adding additional catalyst to it after the fact either, if it doesn't set your screwed. Clean your molds and start anew.



I only measure Alumilite by weight, and I've started doing it in grams since it's fairly more precise than oz.

I have not heated the mold or the alumilite, but my shop is usually fairly warm thanks to being a small, crowded, dirty, unorganized....where was I going with this? Oh yea, small shop, small space heater, works out great when it's colder like today's 47 degrees as the first official day of Fall here in TX. 1 more week and Spring will have sprung until February.

I'm going to look into a dessicant filter for the air compressor, and possibly a heating for the molds and resins. Great stuff! Thanks so much.


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## rocky1 (Oct 15, 2018)

Heat gun from Harbor Freight is only $10. If you're stabilizing, toss them in the toaster oven for a few minutes. Just long enough to warm them up. 

Just be ready to go when using warmed resin or molds, it can accelerate things drastically. As in I have had remnants set in my mixing cup, in the time it took to latch the lid and put air on my mold. Cast came out great on it, but wasn't expecting it to turn quite that quick!


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## TimR (Oct 15, 2018)

I’ll add one more tip someone told me along the way. If you have a vacuum chamber, use it to remove sir from individual parts A and B, before mixing. I’ll keep drawing till I see no more foaming/bubbling. 
Seems I recall B as the one needing some heating to flow better. And of course, watch your shelf life.


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## rocky1 (Oct 15, 2018)

Yeah... and try to eliminate bubbles while pouring too. I believe it is the alumilite instructions that say, to pour slowly from one end of the mold, tipping the mold slightly as if filling a cup of keg beer. Or, it may be Silmar41 website I use that said that, but... it's basicaly about not incorporating air as you pour. It also fills underneath anything in the mold and pushes air up and out, rather trapping it beneath the items in your mold. I realize you can't do that mixing colors, but keep your resin low and close to the mold.


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