Microbubbles on surface of castings

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    • #31651

      Hello, I am using the resin obsession super clear resin, but I have an issue with bubbles. It is not a problem with bubbles inside the resin, but only on the surface where the resin pulls away from the mold after casting–its covered in fine, tiny microbubbles. The bubbles are not all over the entire thing, just the top half of each one is just speckled with them, some really dense, and some still noticeable but not completely covering the surface. The bottom half of the dice are fine, shiny, and smooth. I am making resin dice using silicone molds with a sprue, and when they are removed from the casting, the sprue needs to be sanded off, and thus sanding dust collects in these tiny little micro-holes that I have tried to remove and I can’t. Coating the resin in more resin would ruin the details and warp the shape, and coating in clear acrylic spray does nothing to fill them. Sanding them completely off will also completely remove the engraved numbers. Basically, I’ve done everything I can to remove them from the finished casting, and nothing has worked so I’ve given up saving all my failed castings (about 5 oz of resin in total, and resin isn’t cheap).

      I have tried keeping the resin warm. I crank the heat up in my apartment. I warm up the molds with a small heating pad till they are the same temperature as the resin cup. I mix carefully without removing my stick from the bottom and I scrape the sides carefully. I pour carefully into the molds so I don’t make bubbles. I have tried moving the resin around a little before I fill them all the way up so they coat the sides. I’ve tried it without pigments and still get the issue. I’ve bought different mold release (the castin craft brand mold release and conditioner), and that didn’t help. The one thing that did help with the bubbles was dusting powder in the molds, but it isn’t a good solution because I like the resin slightly transparent with lots of shimmer and dimension, and when I put resin inclusions in it gives a weird slightly opaque color to the resin (not like the surface is dull, the surface of them is very shiny because the molds are shiny. The color of the resin just isn’t clear and doesn’t let the shimmer through and the inclusions look hidden).

      Oddly, when I took my resin stuff to my parents house I was able to use it just fine if the room, molds, and resin was warm. However, that was at an elevation of around 3k feet, and I live around 7k. I don’t know enough about altitude and resin though to know if that might have anything to do with it. It’s also the wet season, and I try to keep my molds dry and it doesn’t feel humid in my apartment with the heat on, but I thought I would mention it.

      Please help, because I’ve been researching and experimenting with no luck. I’m wasting resin at this rate, and I just want to be able to consistently pull cured resin out of their molds without there being a million bubbles and having to toss the set right into the garbage. If I can’t keep spending money on resin to have it go to waste entirely. I also don’t have a ton of money or room to invest in a pressure/vacuum pot or full vibrating table just on the off chance it might work.

    • #31800
      Katherine Swift

      Hi Dallas,

      I’m sorry to hear things are so frustrating for you. It sounds like you are doing a lot of stuff right, so let’s see if we can’t add to that.

      I’m not sure how much the change in elevation is playing with your resin. I suspect it must be something because when I use the super clear resin in dice molds, I don’t have this problem and I am in Florida (sea level). The humidity shouldn’t be a problem as it’s humid here all the time and that hasn’t impacted my results.

      Is there a way you can keep your molds on the heating pad the entire time that the resin is curing? It sounds like the mold may be cooling off before the resin does which can sometimes lead to bubbles. If you can put a dome over the molds to keep the heat in while curing on the heating pad, even better.

      If that doesn’t work, you are going to have to resort to either vacuum casting or pressure casting the resin. Vacuum casting would work here as along has your casting all the way into the sprue of the mold. The vacuum will bring the bubbles to the top of the resin, but they generally don’t pop (think beer foam). You are going to cut/sand the sprue off, so the fact that it has bubbles isn’t a big deal. Otherwise, you can pressure cast the dice which will also get you bubble free results.

      Let me know how it goes for you.

      • #32078

        Hi, I did try it again. I am able to get a few casts out with no bubbles, but there is still the issue. I think it is the temperature, because I put a box over it and on my heating pad and it is a bit better. It’s still not very consistent, even if I do it I can still get bubbles like I said.

        I do appreciate your help though, I’ll try to keep the heat on high and be careful with them, and focus on investing in a vacuum chamber to prevent it entirely in the future.

        • #32123
          Katherine Swift

          To confirm, are you warming the resin in a water bath before use?

          • #32306
            Dallas Lenzi

            Yes, I make sure it is warm. I’ve sometimes over warmed resin actually, making it cure the second I pour it (which isn’t good either). My resin is warm to the touch when I work with it, it’s probably the air being way too cold even with the heater on.

    • #56937
      Ryan Brainard

      I am having a similar issue, but mine is with a pressure pot. I used to cast resin just fine with no surface micro bubbles, but as soon as I started using a pressure pot, boom… I have tiny bubbles on only the top of the dice. I recently got a vacuum chamber to attempt to remove the bubbles from my silicone mold itself to see if that fixes the issue, but it is extremely upsetting to have this result.

      I’d love to know your solution if you ever found one? I haven’t gotten to try the vacuum pump just yet, but I am praying that it will fix my issue. If not, I may just lose my mind haha.

    • #82235

      Im having a similar issue in Australia.
      i have both a vacuum chamber and a pressure pot.

      Ive warmed up the resin as Advised, if i add anything to one of the parts (50/50 mix resin)
      put them separately into the vacuum chamber, and try to pull any bubbles out of the resin part before mixing.
      slowly mix the resin for 2 mins and then pour into the dice molds.
      then put all molds into the pressure pot at 40lbs and leave for 2 hours.
      they are fine for the two hours in the pot, then onto a heat mat for 24 hours to cure (30deg C)
      when i open the molds up… bubbles and micro bubbles on the top most faces and edges of the dice. ?????
      im not using any sort of mold release currently…. HELP!!! lol

      • #82237
        Katherine Swift

        A vacuum chamber is doing exactly what I would expect it to. It tends to bring the bubbles to the top (like beer) where they don’t always pop. Pressure casting is a better choice. Leave it under pressure the entire curing time.

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