Problems making a coaster mold

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    • #12503
      Katherine Swift

      This question comes from Randy:

      I am trying to make some cup coasters using slices of wood as an embedment. I found a container with an indent on the bottom which would make a perfect form to make a mold from. This indent would make a perfect spot for a cup to sit and any moisture to collect without running over the edge of the coaster. However, I running in multiple different issues.

      I had bought some Easy Mold Silicone Molding Putty but found that each time I made a mold, I ended up with bubbles. To practice, I scaled back to making a mold from a metal measuring cup and managed to make a mold without bubbles.
      The problem I found with the easy mold putty is the extremely short working time. So one set of problems possibly fixed.

      I then tried to make some smaller coasters using the measuring cup molds (yeah, I made several) and the molds came out fine but when I placed resin into the molds, I ended up with a very matte and rough finish. So I must be doing something wrong. ;(

      While looking for molds, I couldn’t find any coaster molds on Resin Obsession but I happened to run across some paperweight molds that might be equivalent. The molds look like they would produce a shape like a hockey puck which isn’t exactly what I want (would like a dimple in the
      top) but a hockey puck shape would be close enough.

      So I have several questions.
      1) Will using, for example, Circular Base 492 mold allow me to produce circular coasters with a highly shiny finish?
      There are other sizes as well.
      2) Which resin should I use to make a temperature resistant coaster so a coffee cup wouldn’t damage. I would likely avoid polyester due to smell.
      2a) would this resin be easy to degas?
      2b) would I need to vacuum degas (beyond my ability)
      3) Any specific suggestions for sealing the wood? I’ve tried polycrylic, polyurethane, and modge podge. I like the urethane best.
      4) any other suggestions to get this project moving forward?

      I’m sure that I have many more questions but these are the most important at the moment.

    • #12504
      Katherine Swift

      Hi Randy,

      I’m going to break it down as best as I can with comments and suggestions on what you can do.

      I’m guessing you are trying to make a mold of something that is two to three or even more inches across? If so, I don’t think the molding putties work well for that. I only use them for flat-backed items without any undercuts with a diameter of 1 1/2 inches or less. As you found out, much larger than that and it’s hard to mix and mold the putty before it starts to cure. For items larger than 1 1/2 inches, I would use a pourable molding product. We have a few in our store here: Since it sounds like you might be new to molding, the Composimold product might work best for you. You can remelt and reuse the mold should make mistakes. 🙂

      As for a matte finish on your casting, the mold will pick up the surface of whatever you used as your template. If your template was not glossy and shiny, then it won’t produce a mold that way. I’m guessing your template must have had a matte finish.

      We do have coaster molds in our shop if you are still looking: Some people are happy with the finish with these molds, some want something more shiny. If the finish doesn’t work for you, you can either recoat with another layer of resin or finish with our resin gloss sealer spray. You can find it in our shop here:

      I think circular mold 492 will produce coasters that are likely too large for what you want to do. Molds 431, 893 and 584 are our most popular. You can find them here:

      Since you are using molds, the Resin Obsession super clear resin is what I recommend as it is meant for molds. It mixes in a thin viscosity, so if you are careful in mixing, bubbles are almost never a problem. You can find it in several sizes here: You can see how I used it to make these coasters: You shouldn’t need to degas this resin.

      Wood, on the other hand, is a little trickier to work with in resin. You definitely need to seal it before including it in the resin, otherwise, it will release bubbles which will likely get trapped. Seal it at least twice with the products you mention. I have also had wood people mention they like ‘cactus juice’.

      As for moving forward, it sounds like you have a good grasp on things. 🙂 Jump on in!

    • #12561

      Thank you for responding to my questions. I am trying for fairly large coasters. Some of my wood pieces for embedding are 6.5 inches long. I am also looking for highly glossy/shiny results. Will the plastic molds give me such glossy results? If not, what type of mold or mold making material will? My practice molds were made with a metal measure cup which while not mirror shiny, was at least shiny. However, the practice resin pieces were extremely rough and definitely not shiny at all when using Easy Mold Silicone Molding Putty.

    • #12584
      Katherine Swift

      With wood pieces that large, yes, mold 492 will be large enough for what you want to do. If you are looking for a ‘wet to the touch’ finish, then you will either need to recoat with another layer of resin or our resin gloss sealer spray after demolding. You can find the spray in our shop here:

      All molding materials pick up the surface of your mold template. If you aren’t working with a shiny template, no molding material will fix that.

    • #14498
      Patrick McMahon

      On a related note, I’m curious if you have (and I can’t find) or would consider selling a mold that is like Square Base Mold 584, but with a lip like there is on Basic Coaster Mold 893. It seems like Randy is trying to create a product that I’m also interested in having (although Randy want’s it bigger than for the average coaster). Hoping that you’ll come out with a square coaster mold with a lip to catch condensation.
      Thanks, Patrick

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