I have infilled acrylic in the style before but this is only my third or so attempt at a full rainbow. It’s not the easiest thing to infill in somewhat of a gradient, but I’m learning. I’m finding that isopropyl alcohol and a paper towel work to clean the stubborn bits of paint that won’t clean up off the back with just a paper towel rub. (EDIT!! Too much iso on mirrored acrylic will make it craze!! Don’t do it! I was wrong! eeesh.)
I did defocus the laser for these, from .125 (1/8 inch acrylic) to .15, otherwise it’s all standard proofgrade medium acrylic engrave and cut settings. Sometimes I mix that up but if I’m tired or busy they totally work for this and similar applications.
My one big tip though, for mirrored acrylic if you want to get a much more likely cleaner finish with no heat warping to the mirror backing, paper mask the front AND back. It’s not to keep it clean actually, so don’t do just the side you are cutting from, it protects it from warping and crazing in funny ways on both sides. This is really just true of mirrored acrylic in my experience, masking other acrylics is about protecting from scorching and you can do just one side. I keep the plastic masking it comes with on the front, paper mask both sides and typically engrave from the back.
This was my first attempt at laser foil. I was going mad with this custom order trying to engrave and paint the green sections, and this came out so much nicer. I’m a fan. Wish it wasn’t so pricy maybe we can start a small laser foil mail swap group? I want some silver and gold badly but SO can’t afford a whole roll. I have black to trade
I can’t post more then one picture as a new user so I’ll throw a few into the comments.
It seems to cut just fine on the proofgrade acrylic settings ( I do red because it’s top of the list) for me if it is paper masked properly on both sides. For engrave I play with a few settings, but my current fave is to engrave from the back (so you have to reverse your design and it eats through the grey backing ) at .15 height, 800 speed, 70 power, 270 lpi or 340 if I’m wanting it super clean, but setting the height at double what it would usually be (it would usually be .125), at .15, diffuses it nicely and lets you get away with 270 lpi for most applications and it takes less long
Thanks for replying!! Do you happen to know the exact setting in the proofgrade? It doesn’t let me pick proofgrade because it’s my own material. I am having such a hard time figuring this out!
Yeah! What @Tom_A said, in the top left after you open your file you can click and pick proofgrade materials or enter your own This stuff IS confusing but also easier then it looks, I promise. I suggest trying various searches in these forums about beginning and getting started, there is a LOT of info here.
maybe we can start a small laser foil mail swap group? I want some silver and gold badly but SO can’t afford a whole roll. I have black to trade 
material you’d like.