How to frost acetate windows?

I haven't actually tried it, but thin CA (Krazy Glue) may work for you. I know that it has unintentionally "frosted" clear plastic that I have tried gluing, so it may be able to produce the effect that you are looking for. But take care, it will probably ruin them, otherwise. In any case, it will be irreversible.

I have used Scotch brand (3M) tape matte finish. The kind you use for wrapping presents and such. I use the wider style and put it on the inside of the windows and make sure my fingers don't touch the part that's going up against the window so my finger print don't show through.

Dull coat works great. So does scotch tape. So does does sanding with 200 grit.  

Check the Home Depot or any other bix box hardware store.  The Rust-Oleum Specialty 11-oz. Flat Clear Frosted Glass Aerosol Paint is designed to add a semi-transparent coating to glass windows, mirrors and more. It is great for indoor applications and helps create the look of custom-etched glass when applied with stencils. The paint dries to the touch in just 5 minutes for quick and efficient applications and covers areas up to 12 sq. ft.

Paul,

I used some material I got a lowes it is used to add a frosted look to a window. 

http://www.lowes.com/pd_88113-...__?productId=1103227

You get a lot of material for the price. This approach however makes you replace the material that is already there.  Dullcot or other such sprays as mentioned above might be simpler in your situation.

I use #1000 wet-dry sandpaper to just rub it slightly

Same here......great when you have injection molded windows......

Woodland Scenics makes a product for frosted windows.  

CB&Q Bill

I've done it accidentally with CA (super glue). 

I used a window frosting spray from Lowes. I sprayed this station from the inside. It took less than 2 minutes. 

Bob

Ace hardware sells frosted privacy glass spray. It does a great job.

Lots of good ideas here. Actually any flat clearcoat would work like Testors dullcote, Floquil flat or dust, etc. When I detail my Lionel buildings I replace the frosted windows with clear and use it for other projects.

Pete

Sandpaper works. 

I'll ask the simple question (though it may not be cost effective even if possible).

Did you consider contacting MTH to see if you can buy some replacement windows of one of the types so you can make the large building all the same style?

-Dave

Scotch tape.

there is one that is frosted.

Other wise flat krylon clear coat, but this one tend to shrink the acetate when the layer is too thick.

Andre.

Rust-Oleum Specialty 11-oz. Flat Clear Frosted Glass Aerosol Paint is the only way to go. I just did a big Korber project. It did a beautiful job in five minutes. You can put it on lightly or make it heavier. It has sort of a real light light greenish hue to it, which makes it look like glass.

Trainchief 

Rub some solvent on them

Paul:

I use vellum paper one can buy at any office supply store like Staples. It is already 'frosted'. All you need do is glue in place.

Joe

Yup! 

OOOO super fine steelwool in a circular motion no chance of chemical incompatibility and looks good just cant find a pic to post

Yep, that works great, gives an even covering and takes very little time to apply.

I did exactly that recently on a caboose model I built, as it didn't have an interior and the windows were placed exactly to see that there wasn't one in there...

lazy mans solution.  look in kitchen closet, waxed paper. problem solved.

mikeg

Guys, I used frost colored spray paint that I bought at Lowes.

Vellum paper from Michaels, works very well.  Comes in 8.5 X 11 pads.