Venturing away from clear acrylic for this project.
This is Crystal Clear urethane resin from Smooth-On that I cast from silicone molds (MoldMax 30).
I literally shove the leads for the LED’s through the silicone mold wall to hold them in place while I pour the resin, thus embedding them completely within resin. You can see the tiny air bubbles in the clear resin which I don’t worry about for this particular case as the trophy is for a watersports event. The bubbles kinda play into the theme - or that’s the excuse I’m going with for not pressure casting these.
This illuminated piece is an extra one that I had left over from previous year’s event, so I used it as a sample to test on since the urethane resin was an unknown. I’ve since made some changes to the artwork and will run it at larger scale to fill more of the shape.
Polyurethane is kind of an odd material. First, it does not take on a frosted white look like cast acrylic, it remains clear but it gets kinda interesting. At one power level, you can see the raster lines through the engraving and that catches the light thus making the design really pop. Pump in an additional 10% of power and you end up with a transparent engraving! To this end, urethane is super sensitive to the heat, if you try to make the engraving deeper by adding more power you just end up softening any sharp detail as it melts away.
Here’s another photo of testing samples I ran and you can see it in action.
I should also point out the fact that this testing was ran on an old casting makes a difference. This piece is obviously fully cured at this point but I had also ran tests on a fresh casting only 24 hours old. Urethane generally takes 3-7 days for post-curing to reach its ultimate properties, so the tests on the fresh casting resulted in all of them being clear engraves, and also leaving sticky surfaces behind.
I’m also completely out of space now… the GF has become the newest work surface… BAAAHHH!!!
And here’s what the artwork to be engraved on these looks like, since the shape of the casting distorted the design in the first photo making it tough to make out…