We are fabricating funiture frames with 1 1/2" steel tubing. We degrease with laquer thinner and sand metal with orbital before applying presto black by Birchwood Casey. We wipe off with wet rag and dry with another dry rag before spraying the metal with a two part catalysed polyurathane. THe problem we are having is that clear coat is lifting and taking the blackener with it, leaving the raw metal. I have photos as well. Any help is appreciated. Emmett. 303 507 5275

As far as I know, any oil/ grease left will cause it. I've never had any issues with this particular problem but I never use oil before enamels.

I'm going to take a stab at this one-
I'm assuming you are not getting All the moisture out of the pre finish or the metal. If you have a plumbers torch (small, hand held. O/A is too hot) us it on a hidden spot. Gently, and I mean Gently, heat the area. you will see a dark line caused by the escaping moisture, kinda like the line that creaps back from the front of a piece of metal the first time it has been put in the forge.

The water is acting like a parting line for the finish. As the finish dries, it shrinks slightly pulling the Presto Black loose from the metal. Cold patinas are tuff in that they don't stick very well.
You may want ot contact Birchwood Casey directly to be sure your top coat is chemically compatable their patina.

Oh by the way, Welcome IFI... I see it is your first post.

I wonder if you are looking for the gloss finish if powder coat would work better and last longer? More costly I bet but I know it looks good we have shop down the road that does it for other companies he had me make a few plant hangers for him and he powder coated them they looked good.
Firegnome.
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Blacksmith hammer 50 dollars, steel to make same hammer 5 dollars Aloe plant for the burns free, a day off from work doing what you love. Priceless :)

You will probably have to sand blast the before aplication

I don't think moisture is the problem, I believe it is rust. Most gun blueing or blackening agents work by oxidizing. Steel treated in this manner is a lot more rust resistant than raw steel as it is already coated with a controlled rust surface. My only suggestion to be able to use this method would be to contact Birchwood Casey and see if someone there has a method you can have what you want. One thing I have used for a long time on steel is dark walnut Watco wood stain. That may not be dark enough for you. Last thought is powder coat. Let us know if you find a way to make this work.

I know if I flex a piece of finished material that does not have all the scale removed, sometimes it will pop and take the finish with it, very frustrating.

I guess I should have qualified my answer a bit. I work at a large fab shop (over 30 employees). We patina almost every thing we make. It all gets sandblasted first. Sometimes we damage a finnish a bit doing an install. Guess what? We sandblast it and repatina it. In the field