Contact printing glass. How thick?

Frosted or not, if it's to reduce newton rings shouldn't be a problem doing paper negatives. The paper will be the diffusion.

I use 1/8" glass from a frame shop in all of my contact printing frames. Some have anti-glare and some don't. MY 7x17 frame made in 1946 has the original glass which is 1/8" clear and works perfectly.