So I bought my very first thing of Amazing Mold Rubber and I honestly can’t tell if I’m doing something wrong or the silicone is messed up. I tried casting a blank gameboy deco I had so I could have both a plastic mold and a silicone version, the mold came out perfectly. There was nothing sticky on the mold and it was stiff and thick. I then poured resin into the mold and I let it cure for a night, I came back and it was still bendy and refused to come out of the mold so I let it stay for a night and all day. Then I tried again, it was very difficult to get out of the mold, the sides rufused to come apart from resin. After a few minuets the sides finally came apart and I could take the resin piece out. The resin piece that was in the the mold was sticky, but the area that was facing the air was completely dry and hard. I thought I had done something wrong so I tried casting another resin pour, after the same thing happened I tried making another mold and I let it dry for longer, the same thing happened. I’m not sure what to do. I don’t know it’s fine it’s my resin reacting poorly with the mold or if it’s just the silicone.
Your mix ratio is off....I have had the same issues in the past.
Mix ratios is of the utmost of importance when mixing resin....RTV Silicone is a little more forgiving, but not much. If your plans are to do more castings, then a Gram scale is a must. Mixing by weight is very accurate...more so than by volume. Here are some links that deal with the issues that you are having....read thru them as viable solutions to the problems are provided.
I've had real good luck with my resin pours since I posted the expose with pouring the part "B" into a cup, weighing it to determine how much part "A" and then pouring/mixing the part "A" in the same cup as the part "B" ....the part "A" is not as thick and pours a lot easier than the "B" part.
An exert from the expose.... "I think one the biggest issue people are having is the mix ratios by being off. The closer that I can get to an absolute equal amount of both parts "A" and "B" the better results that I had. MIX NO LESS THAN 1/2 oz. OR 14.1748 GRAMS OF BOTH PART "A" AND "B"...THATS NO LESS THAN 1/2 oz. OR 14.1748 GRAMS IN THE PART "A" CUP AND NO LESS THAN 1/2 oz. OR 14.1748 IN THE PART"B" CUP. 1/2 oz. or 14 grams..thats it , no less."
If your mold requires less than minimum amount shown above, then you need to create some more molds of what ever you think you will need for this project or for future projects.
I'm going to be pouring some resin this weekend...I have some other molds that I have done in the past that I will pour the excess resin in...in other words, the 2 molds that I need poured for my current project require less than the minimum amount of parts "A" and "B" ...so I'll probably mix 20g of each part just for good measure, pour the molds (4 or 5 ea.)
I’m only familiar with the amazing clear cast, but my first couple casts came out sticky. It was due to either my mix ratio being off or I didn’t stir it enough. Now I stir for 5 minutes, whether it needs it or not. Another thing I did, that I no longer do, is scrape the cup into the mold. It’s fine to scrape cup A and cup B, but not once their mixed. Any leftover unmixed resin in the bottom, corner, cup ridges, etc. will be scraped into the good mix in the mold.
If you're using the Clear then it does take longer to cure, I've had Clear that was sticky for well over 24 hours after pouring but cured to not sticky after a couple days. And stirring for 5 minutes is a good idea, it will ensure it is completely mixed plus it will give the bubbles more time to pop before you pour.
Now if you were using RC-3 and it was sticky after 24 hours then there is definitely an off-ratio going on. The only things that get the Clear to cure faster (to non-sticky form) is time and heat.
But yes, you have to scrape all unmixed side A and B into the mix as that will give you an off ratio if you don't. I always scrape all of the mixed resin into the mold and I don't have problems with either the Clear or the RC-3 not casting right.
Is mixing by volume going to be that much different than by weight. Yesterday, I mixed 30gm of part A and 30gm of part B. This was my first casting. It was still tacky after 5 hours in the pressure pot and somewhat flexible. I was casting labeled pen blanks and noticed that bubbles formed after taking the mold out of the pot. Is this normal?
It shouldn't be much difference between mixing by volume and by weight. That being said, I normally mix by volume. If it was Clear then the tackiness is normal after 5 hours as it usually takes closer to the 24 hour mark before it sets up enough to demold. Also I don't use a pressure pot so it might be different but I've heard that the bubbles aren't supposed to form when using one - again, it's just what I've heard and I have no real experience with it.