I just recently got a batch of alumilite slow clear and had great success casting but wanted to eliminate all bubbles so I got a vacuum and a pressure chamber. Doing some tests I keep getting this white layer on the exposed resin and clear through the rest of the mold (covered parts). I have been doing tests and all casts outside of the pressure chamber are clear with bubbles and all inside the chamber are bubble-less but with the with layer. Thinking it was moisture on the air compressor I have taken several steps to dry the air and its somewhat better but it is still cloudy. So am I on the right track or am I missing something else? Is the resin that finicky with moisture in the air?
Post by carol - Alumilite Corp on Mar 1, 2016 8:47:08 GMT -5
If they are streaks or whisps of cloudy, make sure you are mixing and then over mixing the materials as this could be a swirl of A side which would phase and turn white/cloudy.
One example of how we've noticed this is when we've used cups with grooves on the side rather than straight walls. So make sure you are mixing in a straight wall cup ... not a Solo type cup with ridges/grooves on the side. Reason being ... your stir stick will not be able to scrape/mix the material in those groves and then when poured you have either A side or B side that is unmixed that pours out of those grooves and into your mold which will leave streaks that can turn white or cloudy which might be described as whisps.
These are not whisps which I have encountered on occasion. This is the entire exposed surface turning white. So once poured into the mold, whatever surface is exposed to air goes white while the resin unexposed stays clear.
Post by carol - Alumilite Corp on Mar 2, 2016 16:59:50 GMT -5
That more than likely is the tail end of your pour that is not completely mixed as the first portion of your resin cup. The air really shouldn't have anything to do with it turning white, unless it was foaming moisture white and that could indicate some moisture contamination Mendeznm. Please try again by mixing as describe above and let me know if that white is still on top. If so I would be happy to bring it back and test it here for you Mendeznm.
As stated before. I have done several side to side comparisons and they all exhibit this behavior. When left outside crystal clear with few bubbles. When pun on pressure pot the white haze. Will do 1 more round and take pics. Should I leave the cast to full cure under pressure or just the demold time?
Left my samples overnight in my kitchen and they cured with the frosted layer as discussed. They were clear after demold time. Starting to think is not related to pressure pot snd more with humidity in my house. Thoughts? Mixed As follows: measured in 2 cups equal A and B. Poored A into B. Mixed until clear and scraped and re-mixed. Poured into new cups for test. This should have provided slightly less A and avoided any unmixed parts. What could I be missing? I also did a bigger casting with coloration and that one looks fine, thinking size could be an issue as well?
When I say cups, I mean mixing cups. We are talking mixes of 1oz to 4oz total mix. 30 grams to 100 grams. I think I got better pics for you. I will call on Monday to discuss. I now believe it mightbe temp related as well. See pics.
Post by carol - Alumilite Corp on May 9, 2016 14:08:53 GMT -5
The white wisps have only happened for only a few issues. Measurement, must be 1:1 by weight (making sure scales are working properly) if there is too much A side you can get the white wisps. Mixing: must be mixed and blended well so the chemical crosslink can take place, all of the A side meets all of B side for a complete cure. When mixing make sure you scrape the stick off as I said earlier and re mix that back into the mixture, several times.
The only other thing Mike is sometimes moisture, will/can cause some white, but usually then there is some bubbling/foaming, or tiny white porosity bubbles in it. The pictures you sent don't look like moisture issue.
I too am having the same issue. When the casting comes out of the pressure pot it is clear, but within a few hours it starts turning cloudy and after a day or so it nearly opaque. Is this a sign of the A side and B side not crosslinking? I did a large casting a few days ago that came out perfect, but my small castings have all been failures. My scale claims accuracy in tenths of a grams and I try to get equal amounts of each, though next time I'll err to the B side. The B side is getting thicker, so I'll try warming it next time. Also, I fill both bottles with argon after casting. Any other suggestions?
Post by carol - Alumilite Corp on May 11, 2016 13:58:24 GMT -5
Yes do thin it with heat (in a pan of warm/hot water, not boiling) cap on tight. If your scales are good it is more than likely in the mixing of that small of an amount. Mix well, scraping sides in a smooth sided mixing dixie cup. (not in measuring cups that have the graduation tabs in side of them) Make sure blended well, scraping stir sticks off a couple of times re blending that mix in with the resin several times.