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Mold for Polyurethane Resin? Answered

I purchased a Polyurethane Resin mix (Part A/Part B) to create a guitar. I’m wondering though what material I can use to create the Mold? I normally work with Wood, so this is all new and exciting, but oh so confusing. Can I create a mold out of wood and coat it with a silicone spray? Do I need to use some other non-porous material?
Any insight would be excellent.




8 years ago

Well... so I follwed your silicone spray idea, mixed the chemicals, and got the expected results.... no good for this application.  The final mix turned into a yellowish-opaque product that does not meet my original expectation.

So.... on to the new idea using the Plexiglas...  either:
1) Cut out 10 or so guitar shapes (depending on thickness) and build up from there.  Good thing of this idea is that I can cut out and put in pictures sandwiched between sheets to give em a cool 3-D look

2) cout out 2 guitar shapes (need to have relatively thick plexiglas) and use metal spacers between the two to create the right thickness. 

Both of these should look nice, but the tone is going to be terrible. Active pickups and/or piezzo pickus will be a must. With option #2 I can potentially sandwich a resonator box between the sheets to give it some tone.  

Anyway, thanks for the input 

Hmmm, you might have been better off getting a big chunk of plexiglas or acrylic plastic and carve/machine the guitar body if that is what you are making.  You might have some problems in trying to get a completely clear body if you do not vibrate out the air bubbles - microscopic ones, control the cure, and polyurethane I think cures to a yellowish color over time.  You will experience shrinkage too so you might end up with a warped body or uneven cure that looks like a dried out pumpkin. You could look up mold release agents and see what is normally used for resin casting.  Anyway, you might be using a gallon or more of the expensive resin stuff to actually fill the mold.  Let us know how it turns out.  Good luck.

Ugh!  Well... let's see what happens with my project.  I'll take some pictures and post.  The yellowing is a bit annoying though.  Didn't realize that that can happen.  Thanks

If you're prepared to sand & polish, you could line the mould with cling-film. A well-made mould sprayed with silicone would probably work though.