Does refinishing Damascus barrels in either black and white or re-browning impact the structural strength of the barrels, particularly the rib joints? Is it necessary to drill holes in the bottom rib when refinishing? Finally, who out there is doing good quality black and white refinishing? Thanks.

Traditional slow rust blacking or browning of Damascus barrels should do nothing to harm the integrity of the barrels or the rib soldering joints. It is hot caustic salts bluing that is detrimental to soft soldered double barrels.

Many barrels have less than 100% solder joints, and some water or etching solution may get inside during the boiling, etching, or rinsing process. The rusting solution is typically put on very sparingly, and should not get inside. Many people think drilling a weep hole to flush the area between the ribs and barrels is a good idea. It doesn't hurt anything, except providing a clue that the barrels have been refinished. But simply doing a good neutralization and rinse, and then drying the barrels in a very warm place will vaporize and drive out any traces of moisture within. That entire area is typically well tinned during soldering, so worries about unseen corrosion continuing after refinishing are overblown in my opinion.

The greatest potential threat during browwning is the amount of metal removed when striking up the barrels prior browning. Repeated re; browning of barrels over the life of an old gun can result in a reduced wall thickness. According to various sources recommended minimum wall is .020!

There is NO need to put weep holes in barrels. It is enough of a pain in the ass dealing with them from makers who did it originally. And the ones who didnt... why do it now?
Remember... the process used to refinish the barrels is the exact same process used to finish them originally. So... who would it do harm?

It will show poorly soldered ribs. It will hurt nothing.

If by "it" you mean drilling a weep hole...

Drilling a weep hole, especially on barrels that were never drilled at the time of manufacture, smacks of a novice job and encourages the question "what else was improperly done?"

Re finishing will not impact the structural strength of the barrels, or the rib joints, no drill holes are needed, and you should never finish barrels in hot salts tinned or braised.

Hot Salts do not affect brazing nor lead-free solder. It doesn't look right on a double regardless & as stated should Never be used on one with lead solder joints. They will also eat up anything of aluminum in short order.

True that. If you own a fairly modern Spanish, Italian or Turkish gun...it’s going to have brazed ribs and the barrels and furniture metal will have been hot salt blues/blacked. And virtually all furniture is finished using salts. Nothing to be afraid of if they (hot salts) are used properly and the metal is prepared appropriately. Fresh salts often give the best finish.