>I have also used ferric chloride to etch a dial in brass, and while it does >work, it takes a great deal of patience and/or skill to produce a >satisfactory result. A clean mask is critical to success. In addition, I did >not etch the design deep enough, and now that the brass is weathering, the >dial is barely readable.
Ferric chloride is tricky, but preferrable to messing around with acid. I find that getting a good quality etch resist is of paramount importance. The photographic process is tricky, but with a lot of trial and error good results can be obtained. Like anything, the more you do, the better it will be. For manual etching I have experimented with a number of substances including wax, nail polish and oil paint, but the best so far seems to be roofing asphalt thinned by a brush cleaner to the desired consistency. A high degree of detail is possible. As for the etching process itself I find the best way to do it is hot and quick. I have the Ferric chloride at about 50 deg C, agitate it frequently and try not to exceed 15-20 minutes etching time. I found that beyond that the solution begins to lift off the resist and you loose sharp definition and fine detail. Also in places where the resist is a bit thin it seems to penetrate the resist and discolor the parts which are supposed to remain intact. I tend to get rid of it by polishing afterwards with a felt wheel and a green componund which I buy for honing of sharp tools. However, if one is heavy handed one can take off too much brass and the result is very much as you describe - the relief becomes too shallow. By the way does anybody knows how to get color into the negatively etched lines (or for that matter engraved lines). I tried gun blue but it will not stick. Some of the patinas give nice blue colour but it tends to be uneven (as you would expect from a patina). I hear the jewellers use stuff called niello for this purpose, but I have never tried it. I now tend to etch the lines as well as the numbers as positive, ie they stand out from the base. Finally does anybody think we should form a newsgroup? Mike Koblic, Quesnel, BC
