Liver of Sulfur Help

[Laggard]

This may be the dumbest question ever but here goes.   I can’t get this to blacken brass.   I’ve tried room temperature water, I’ve tried scalding water.  I’ve left copper pieces in there 10 minutes and overnight.  Nothing.  I’ve even tried different ratios of water to sulfur.  
 

Thanks!

[Bill Hudson]

Be sure to degrease your brass. Handle it with tweezers.  Heat water to nearly hot and kept there, dissolve LoS in water. Heat the brass to quite warm and then dip it into the solution.  It takes quite  while for the brass to start turning.

[AON]

I've found that LOS does not seem to react with brass.

Bill wrote that it takes a long time.  If so it takes much longer than I am willing to wait.

It works extremely well with copper.

[gjdale]

I’ve always understood that LoS was for use with Copper, not Brass. For Copper I use LoS in a gel form and just put a little in small pallette and add some water next to it. I then use a paint brush dipped in the solution where the water and LoS gel are meeting and rib it onto the part. It works extremely well. For Brass you need one of the Selenium based solutions such as Birchwood Casey Brass Black. The other one that I’ve used successfully with Brass is Jax Pewter Black - gives more of a gun metal finish than black, but very easy to use. Again, I’ve found that rubbing it on with a paint brush works better than dipping the part.

[allanyed]

As above, LoS  does not blacken brass easily if at all.  Copper, no problem.   I have gone to copper whereever possible, but when I do need to use brass, pickle it, rinse it  and blacken with Birchwood Casey (or similar products) since my favorite, Blacken It is no longer available that I can find.

 

Allan

[Laggard]

Thanks all.  I can paint the brass but find that the paint peels off too easily.  

[AON]

Try a black permanent marker.

Check that it doesn't rub off with your finger.

[Roger Pellett]

Industrial metal fabricators have long been faced with the problem of painting metal with a durable coating.  Industrial painting specifications invariably require using a solvent to remove grease, oil, etc.  This is followed by abrasive blast cleaning with sand or if possible metal grit.  Most specifications then require prime coating within the same 8 hour shift.

 

So what does this have to do with the question at hand?

 

The principals are the same.  First, go over the surface with a file to get rid of solder, scale, etc. A file or sandpaper will also give the surface what is known as “tooth.”  Coatings do not stick to polished surfaces.   Thoroughly clean the surface.  An aggressive solvent is necessary. I use a little lacquer thinner in a tuna fish can.  Handle the part with tweezers.  Oil from your skin will inhibit bonding.  Blacken or paint immediately.  An invisible oxide film can form overnight.

 

These small parts will usually be handled after coating.  To avoid damage, I seal the coating by spraying the part with a matt lacquer.  Dulcote or similar.

 

Roger

 

 

[mtaylor]

I see you are in L.A.   Head to a local gun shop as they usually have the Birchwood Casey products.

[Bill Hudson]

Maybe my posting on LOS was misleading. I did not understand you were attempting to blacken the brass.  That will never happen with LOS it will only darken it. There are several products on the market that will blacken brass. I use Hobby Black which I found at the local hobby shop. Also Old Number 7 cold brown (gunsmithing)  and the cheapest is Novacan black patina developed for stained glass work.  I find it at local craft houses. Most of these are nitric acid and selenium compounds. Be sure to wear rubber gloves and eye protection and good ventilation.   CAUTION:  All of these kinds of darkening products are very poisonous.  Use ventilation when using. Also a warning, keep the cap on the bottle when not in use as the acid in them will fume and turn all your bench tools; drill press etc. a nice brown patina. (don't ask how I know). I have made my own using copper sulfate.  https://chestofbooks.com/reference/Henley-s-20th-Century-Formulas-Recipes-Processes-Vol1/Black-Color-on-Brass.html   

Edited October 17, 2021 by Bill Hudson