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Hybrid Vinegar Patination


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Client up in Kern County wants some rusty samples. He will receive some rebar, excavated after 47 years, and some rusty dia. 5/16" wire rope, patina age unknown. I decided to try my hand at rapid patination,  so I immersed a very clean dia. 1-1/2" 52100 bearing ball in 40% vinegar for 8 days. Over those days, the solution went from clear, to claret, to blue, to blue-green, to black. The reaction was still vigorous when I removed the ball:


I then wiped down the ball - pretty dark grey, and encased it in vinegar soaked virgin gabbro semi clay.  It sat for four days in 90°F sun (not nights, this aint Floridia). Here is what I got:



Next one with be straight into the vinegar clay, to maybe remove a step.

Robert Taylor

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Actually I was interested to know if you planned to duplicate the finish on a 52100 knife blade and hence used the bearing as a test vehicle. Besides bearings and knives I don't know much that alloy is used for. 

I was asked to duplicate an early 19th blade once and to make it appear as if it had the same patina on it as the museum piece.  I was willing to do so; but on the inside of the handle scale I inlet the year I made it and embedded lead solder---if it gets xrayed it will show it's not "original".

(I've had a number of discussion with various reenactors trying to point out that if they got a blade or other piece of kit for their portrayal it should NOT look like it was centuries old.  It should look like you had bought it new within the last couple of years.  (At the medieval technology conference, Penn State a couple of decades ago; there was a very interesting presentation by Dominic Tweddle on the Goldsmiths house in York that they had just finished restoring about the same issue---everything was to look new and recent except for one chest that was listed in an original inventory as having been inherited and so it was made to look a generation older.)

Higher temps == faster chemical reactions which are sometimes good and sometimes bad to get the patina you want.  Old crock pots are often handy to hold solutions at warmer temps but PLEASE mark them NOT FOR FOOD USE! (Slower reactions are sometimes denser and more adherent than faster ones which are "featherier" )

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I have only begun to "experiment". I am an uncredentialled amateur, but I do know that in general, raising the temperature often accelerates the reaction.  I do not know about sodium hydroxide, but Keep in mind that mixing common household chemicals can result in unwanted violent reactions.


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Or toxic fumes, (ammonia and bleach for instance.)     There is a smith in Northern New Mexico who makes up a lot of stock and then has it naturally patinating out back of the shop for years to get a good adherent rust patina.  (Last time I visited him he had just finished a US$90K commission.)

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One of the demonstrators at ABANA in  Richmond talked about his "drainage ditch patination process". I guess it takes a little longer. New England School of Metalwork suggested a spray composed of (if I remember correctly) vinegar, salt and hydrogen peroxide. Just spray it frequently on your piece for a few days and a nice crusty patina builds up.


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