Optics and cushion foam

I am building a 6" long focus refractor and have made a carrying/storage case
for it. I would like to cushion the inside with foam rubber (like what is
inside cheap cushions). I seem to recall that the out-gassing may cause a
film to form on the lens. Is there any chance of that happening?
thanks,
-Jon

Jonathan Lingel said:

I am building a 6" long focus refractor and have made a carrying/storage case
for it. I would like to cushion the inside with foam rubber (like what is
inside cheap cushions). I seem to recall that the out-gassing may cause a
film to form on the lens. Is there any chance of that happening?
thanks,
-Jon

Hi Jon,
The high density gray foam should be pretty stable. It can break down, but there's a cure. Trouble is I don't recall the name of the product. It looks like sulyfane, but is far less sticky, and soft as can be. You keep caps on the optics and cover either the scope or the foam with the soft plastic. Model railroad guys use it for fine brass locomotives.

What lets off gas is inexpensive silicon caulk. Don't seal a case with it. As it cures, it smells like vinegar. That's a mild acid at work on everything inside. Use urethane.
Hope that helped a little,
Steve

It's best not to let foam contact any optical surface. The manufacturing process for most consumer-grade foams guarantees there will be inclusions of dust and grit. Melamine foam (used in magic erasers) is actually a super-fine form of sandpaper, and it should never be used for cushioning.