The end goal of this project was to emulate a standard fluorescent tube, and to do that the light coming off the tube would have to be very even. I tried a few different methods for diffusing with mixed results. Unfortunately I didn't take any pictures of the progress as they weren't working as well as I'd hoped...

Methods tried (so far):

• Sanding the outside of the acrylic tube
• Very thin coat of white paint
• Spray on frosted coating (Rustoleum type stuff)
• Under cabinet diffusers that are used in kitchens

This one probably worked the best, I sanded with I think 220 grit in multiple directions. I sanded length wise, radially, and then in kind of an angle. Maybe this combined with something else like tracing paper would work well.

Thin coat of white paint:

I was hoping this would give a fluorescent tube appearance and help in diffusion, but the light just ended up exposing every small imperfection in the paint job. The theory behind it was that maybe the white paint particles would give the light something to bounce off of and emulate actual diffusion material.

Spray on frosted coating:

Again, mixed results. Worked a little bit but I'm worried the coating isn't that durable, and when I tried putting a clear coat over top, the frosting effect disappeared...

Purpose made diffusers for strip lights:

Turns out stuff built exactly for your application works pretty well. Who would've thought eh? More seriously, this stuff worked fairly well with some modifications, but would need to be combined with another method to give a smooth 'white' exterior finish. Perhaps this and some tracing paper or diffusion film?

Other (untested) ideas:

Using diffusion film common in the sign industry. Can't find a supplier for this yet though :(

I also ordered some 140 degree 5050 led lenses from china that I was going to try and sand down to diffuse to see if that helped.