Friday, March 16, 2012

Texture and Patina

One thing said about craft masters is that they are in control of their tools and techniques. That is what skill is all about. But when it comes to the issue of surface patinas watch out.

Early on in my metalworking experience I was visiting with an artist who said he never agreed to create an exact color surface for a client even if they had the target example in hand. Under no circumstance would he accept an color image. At the time I didn’t think much about it but it wasn’t long before the complicated relationship between the alloy, the surface texture and the finish chemicals sunk in.

My first work taught me something about the differences which can result from fire scale effect differences between the coal forge and the gas forge. The “tooth” and gross texture differences between hot wire brushing, pickling, planishing, sanding and tumbling are remarkable.

One of my first really difficult struggles came when working with a sheet of hot rolled A36. Apparently the alloy differences in the surface made it almost impossible to get an even color with hot waxing. I think that may have been when I started experimenting with spraying Minwax polyurethane instead of rubbing with the paste wax.

More recently I have seen a similar problem with creating a rust patina with hydrochloric acid and hydrogen peroxide on A36. If the pieces are from two different batches of A36 the problem is magnified.

The chandelier and pendant images illustrate the color variation due to (in addition to the camera) the different metal stock alloys in the tube, sheet, flat bar, balls and chain, and the surface texture differences between the glass sockets and the smoother tube.

Now that I am aware of some of the potential bummers I have somewhat more control of the process but, really, I don’t mind the help of some serendipity.

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