Flattening agent for polyurethane

[Edward Dyas]

I read somewhere that a person can add talcum powder to oil based polyurethane as a flattening agent. I was wondering if this was a bad idea. I tried it on some scrap wood and it does mix into the poly and doesn't make it cloudy. What I don't know is what it would do to the long term duribility as compared to the proper flattening agent. Where I live I can't get flat polyurethane or the proper flattening agent either.

[Bob Wingard]

It might work as you suggest, BUT, be aware of it's downside ...

http://www.nlm.nih.gov/medlineplus/ency/article/002719.htm

[Sam Stephens]

how flat do you need? the common way to reduce the sheen to a satin is to "rub it out" w/ 0000 steel wool after it has cured (at least a few days to a week if not a month). you can use either wax or mineral spirits as a lubricant. my other suggestion is that the final coat has the most impact on the final sheen i.e. you can use gloss for all coats and then use a "reduced" sheen for the last and achieve the look you want.

[Edward Dyas]

What I would like to do is take satin which I can get and make it dead flat.

[Scott Holmes]

800 grit sand paper is what I would call dead flat...


I think the talc would end up whitishor cloudy though I have not tried it. I have used Shellac Flat as a flattening agent in varnish and shellac.