doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com My first damascus refinish...

I've always used ferric chloride for the acid dip, then a browning. After enough coats it can be boiled in log wood to get a black and white color instead of brown and white. I've never heard of anyone useing copper sulfate. To each his own. Paul

I am no expert but I have not used any copper sulphate compounds in my browning since my early trials.
I found that it cut into steel as well as iron which could 'muddy' the final contrast. It also tended to promote after rusting which has not been a problem with the boric acid etch that I use now.
Another problem with copper sulphate is that it precipitates copper deep into pits and engraving which can be the very devil to remove. In one particularly bad case, I had to use a concentrated nitric acid bath to remove the copper which made a mess of the base metal as well. The air was blue after that event!
Yet another problem is that unless all the jointing areas are masked with varnish or paint, if a full immersion is used, the copper sulphate etch can actually loosen the jointing of a border line jointed gun to the extent of rendering it loose. Same can be said of using Ferric Chloride in a full immersion.
This can be avoided by applying the concentrated solution by cotton pad only to those areas that you wish to etch but this is tricky and very difficult to keep off breech ends etc.
This is not to diminish the great results that have been achieved by Cadet and all others that use copper salts for their etching, it is just beyond my modest abilities.

Thanks all for the feedback, comments and ideas.
Consensus seems to be that CuSO4 isn't the way to go; I was just following the instructions on the bottle! There seems to be plenty of different ways to arrive at the end result, and I probably will do things a little differently next time.

Toby;
I had wondered about using Boric Acid, but have not tried it. Can you give a few more details as what solution & how long do you etch with it. It is comparitively mild I believe in comparsion with the other acids mentioned.

Chemically, what's going on in the CuSO4 bath? Is it etching (eating metal away), or is it actually electroplating a layer of copper on, which is then later eaten away by the browning solution? I remember words like anode, cathode etc from y11 chemistry, but that was half my lifetime ago, and I didn't pay enough attention or do very well at it!

cool

The SO4 part of the Molecule is derived from the Sulfuric Acid treatment of Copper and it of course etches metal, but the real problem in my opinion is the layering of copper on the barrel which accopmlishes nothing but aggravation. As Tony said above, it is unnecessary and only a problem

Never having browned barrels myself (other than flintlock rifles) I am nothing more than an observer. However, after having studied many original damascus finishes that disply a brilliant contrast and are high gloss (no, they aren't varnished) and perfectly smooth I have a hard time believing any form of etching was used on them. What say ye?

2-Piper
The Boric acid etch comes direct from Angier's book and I don't think I do anything out of the ordinary.
I use a stainless steel bath, dissolve boric acid powder in distilled water (clean rain water would probably do) to about 5-10% w/v. This gives a saturated solution at about 50-80 deg C.
I grease the inside of the tubes, plug with hardwood dowels, carefully degrease the outside with whiting (you must do this thoroughly as the boric acid will not work well with a contaminated surface and once oil contaminates the solution one really has to throw it out and make a new batch).
I then warm the solution to 60-80 deg C and lay the barrels in the solution for between 30 min and 2 hours.
It is very gentle but if the surface is clean it quickly mattes the surface showing the full pattern of the damascus. After a bit longer, carbon from the steel starts to darken the surface and can make the pattern harder to see but a brush with a gloved finger wipes it away and all becomes clear again.
When the pattern is distinct over all the surface, rinse with fresh tap water, remove the plugs to check the bores are still dry, if not dry out, re-plug, degrease and start your browning.
The solution does not last for ever and needs replacing once you notice that the etching is getting too slow.

Toby;
Thanks, from Angier's book was what had caused me to wonder about its use as an etchant for damascus. As I recall he just mentioned it for removing the old browning, rust etc prior to polishing but not per se as for bringing out the pattern in damascus. From his description it struck me it could be uised for this purpose. Thanks for confirming that.