Ok this morning I finished my mask mold for one of the Mortal Kombat masks and I like to cast these with a couple layers to prevent any cracking or breaking. The first layer went on good no bubbles but when I went to put on the final layer the second layer I ended up with a lot of little air bubbles pretty much covering the top of the back side of the mask, should I be worried? I know I've heard of microbubbles being used in casting before but with my Noob Saibot mold this did'nt happen, is it the resin or something wrong with the mold?
What's wrong with my resin?
- Thread starter PepMaster
- Start date
Smoothcast 300 with a So-Strong Black dye, mixed properly, just finished raining outside but I was working in the shop behind the house, I'll get a photo up in a second. The mold was washed out as well and dried before any casting was done after it came off the master, which was a finished pepakura mask. That's what I'm guessing as well Alan.
mvmagic
Well-Known Member
I don't think its a mold issue if the first layer-which is in contact with the mold-didn't bubble. Maybe you just mixed in too much air? Air humidity can also cause that, as can do temperature changes. Did you leave the mold in direct sunlight? Or some other heat sources perhaps? I've had bubbling issues with old resins as well.
exoray
Master Member
That is likely your problem, moisture contamination due to high humidity... The humidity inside a shop or outside is the same unless you are removing or adding it artificially...
Unlikely to be moisture - just air that was mixed in. (you were probably a lot more gentle mixing the first batch or it degassed while pouring). If the mold is open faced and has the back exposed, this can be totally eliminated by quickly passing a mapp gas torch flame over the resin before it kicks (it is the resulting gas from the flame that eliminates the bubbles - not the flame itself, so the flame need not touch the resin). The result will be a surface like glass.
See when I pour the resin into my mask mold I put it in the center of the mold then just tilt it back and forth to coat all the areas of the mold, when I do this there are not any air bubbles that I can see in the liquid, but when it's starting to cure is when they come up.
mvmagic
Well-Known Member
That can easily happen when slush casting. As you slush the resin, you're trapping air in it. I used to have that with open molds-sometimes with degassed resin even (this is what lead me to believe I am trapping air while slushing) but when I learned the torch trick Superkrates mentions my open mold castings have been fine.
exoray
Master Member
Why do you say that? I have personally experienced the same problem on high humidity days, and with moisture contaminated resin... Trapping high humidity air even makes it worse... I know for certain that humidity can play games and produce exactly the effect he is describing, but a picture would certainly help verify it... Some resins are more tolerant to the moisture and work find on a high humidity day, but I have had some plume like a volcano and foam right out of the mold on a high humidity day...
Here is an example of normal trapped air from mixing (left) and moisture contamination on a rainy day (right)
If you cut a cross section of the moisture contaminated part on a saw you will see pinhole bubbles everywhere throughout the entire piece... The one on left you just shave off the top layer and the rest is solid...
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irishamericanlad
Sr Member
i agree with exoray, when it gets stupid humid here in texas, and if im not in the shop where its cooled and regulated, thats excatly what happens to my pours, it boiles over and hardens into a brittle piece of pooh sickle lol if your pours are small, and your house is air conditioned, lay out some plastic bags and try your pour there... even the smallest amount of moisture will effect the pour...
I've also noticed the same thing happening if I have a large container of resin that is only partially full. The moisture builds up inside the container. Might not be the case here since the first layer had no issues. But a pointer nonetheless - only buy as much resin as you plan on using on your (current) project.....
Gene
Gene
exoray
Master Member
Here is the result of pouring out the measured A + B portions and then getting distracted before mixing and pouring into the mold on a rainy day...
A cool effect if you want lava rock
exoray
Master Member
Go to a higher end wine store and pick up some canned wine preserver, and give each jug of resin a burst before you cap it... Most resin suppliers also sell canned preservers as well, or you can just get a container of inert gas like pure argon (not a Argon CO2 mix) that contains no Oxygen to blanket the containers...
I have been vacuum boiling the contaminants out of any resin that has been sitting and starts acting up... I hear you can also simmer it on a hot plate to boil the water off, but I have never tried that as it just sounds nasty...
irishamericanlad
Sr Member
they make the casting very brittle, its not a product i would put out or sell, but if its yours for your own self... but trust me when i say you will feel alot better to fix this issues now...
exoray
Master Member
Yeah, I boil each half under vacuum (29 inches of mercury) for about 15-30 minutes... And remember it will expand 2-3 times in volume while under the vacuum...
In your case if the first layer was fine your resin might also be fine, just wait for a less humid day or get a dehumidifier for your work area...
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