Adding Patina To Brass

[Nomad]

I'm developing an interest in adding patina to brass for a couple of reasons. One is to make a new belt with a non-shiny buckle, and I had ordered a couple of buckles from LePrevo when I had ordered leather a while back. I decided to have a go with a buckle held over a bath of vinegar and salt to see what happened - and nothing happened. It turned out that the LePrevo buckles are lacquered, which was confirmed when I tried to measure resistance using a multimeter - got an open circuit, telling me the surface had an insulator on it. I tried wiping it with Acetone to no avail.

I did a bit of mooching around and ended up choosing B&Q's own-brand Diall paint and varnish remover (which I had seen working well in some YouTube vids, where someone restores toy cars). A small dollop of this was put into a plastic box and a cheapie small brush used to paint it over the buckle. After a couple of hours, I thought I could see some bits of the brass darkening in places, but wasn't sure if it was just the clear lacquer discolouring, so I left it in overnight, then flipped it over and left it another night. I just took it out of the box and gave it a scrub in some warm soapy water.

Here's what I used...



Cheapie plastic boxes from Tesco (3 for £2), and even cheaper toothbrushes from Morrisons (2-pack for a mere 30p!), and 500ml of Diall stripper at £3.80.

Here's a before and after...



Untreated buckle on the left. The dark bits are reflections - it's all clean, shiny brass when you wiggle it about in the light.

A closer view...



The patina has exactly the sort of old, antique look I was after, even though I wasn't expecting it. There are a couple of small spots that are still shiny (perhaps missed when slapping the stuff on), but these seem to be more conductive than the untreated buckle, albeit still needing a little pressure from the meter probes. The areas with the patina readily show a short circuit (so it's not a coating of discoloured lacquer).

I've added a little bit of the stripper darken the shiny bits...




I'm really pleased with this unexpected result - saves having to experiment with various chemicals to try and get the dark brown style of patina (which I think involves using Sulphur in some form).

I still need to see if there's a time period where lacquer or paint can be removed without adding patina (I have a brass thing that I want to remove paint from, but want the option to choose whether, or how much, patina to add). Also want to see if it takes less time to get a nice antique look like the above using the Diall stripper. Another thing I want to do is see if I can get a verdigris type of patina that's robust and stable, rather than the crusty structure that seems to be quite common.

 

[crosslandkelly]

Looks good. I'm not keen on that shiny brass look either.

 

[Nomad]

I think shiny can suit some things (like a restored paraffin pressure stove), but patina also works. Generally, I like it if something starts shiny and gradually builds a patina (but I suspect that was very unlikely with the buckle from LePrevo).

Discovered a little more.

When I put the buckle back into the box with paint stripper on the remaining shiny bits, I also added a little offcut of plain brass that I know hasn't been coated. I wanted to make sure that the patina on the buckle wasn't some weird chemical reaction that requires the lacquer to work. I just had a look at it, and noticed that it had become patinated around the edge of the blob of paint stripper. I wiped some away to find that it was still brassy underneath...



Original slightly patinated finish on the left, and the dark bits are where the stripper was quite thin. This looks to me like oxidation or drying of the stripper is part of the process - the thicker blob of stripper will still be moist and/or prevented oxygen getting to the surface of the metal. If that's the case, then the bright bits of the buckle maybe had particularly large blobs of stripper on them.

I wiped the rest off and spread a thinner coat on it...



The buckle has started to darken a bit, but not as much as the edge of the blob on the offcut...



These have been in the box for a bit over four hours. Given that the thinly coated parts of the offcut are already pretty dark, it's looking like this will be a fairly quick process once the coating thickness is worked out (well, quicker than two days at any rate). It's also interesting to note that the dark bits of the offcut are comparable to those on the buckle, which suggests that it doesn't darken beyond a certain point, perhaps due to exhaustion of whatever is causing the effect, or maybe the patina acts as a barrier layer which impairs the continuation of the reaction.

 

[Klenchblaize]

I would have used a blowtorch to remove the lacquer.

K

 

[MrEd]

i have made a few brass things, and have used 'brass black' to age or darken them. The things i make go almost to the black though, but you can take it out of the solution earlier for a lighter finish.

https://www.ebay.co.uk/itm/Birchwoo...var=640122345949&_trksid=p2060353.m1438.l2649

 

[Janne]

You can either use urine ( ammonia) or hard boiled eggs.
Method 1: wee in a plastic bag
Place throughly cleaned and de fatted brass inside, close, make sure urine covers all brass

Method 2: hardboil a couple of eggs. Let cool, remove egg yolks.
Crush the yolks, cover the throughly cleaned and de fatted brass with the eggyolk paste.
Place in plastic bag, close.

Note: the brass must be as cleas as it can be. Fingerprints ( fat) can leave marks, so wear gloves
,

 

[Broch]

Another thing I want to do is see if I can get a verdigris type of patina that's robust and stable, rather than the crusty structure that seems to be quite common.

Maybe not as drastic as this though? Used a ferric chloride solution - it cleaned up reasonably well leaving a 'sensible' level of patina

 

[Nomad]

Just took the bits out and washed them...



This is about 5 hours after they went back in. The offcut was showing signs of darkening after about a couple of hours, while the bright bit on the buckle seemed to be going more slowly. Still a bit of shine on the buckle, but I'm happy with it.

Closer view...

 

[Nomad]

i have made a few brass things, and have used 'brass black' to age or darken them. The things i make go almost to the black though, but you can take it out of the solution earlier for a lighter finish.

https://www.ebay.co.uk/itm/Birchwood-Casey-Gun-Restoration-Refurbishment-Solutions-for-Stock-and-Barrel/370893617303?ssPageName=STRK:MEBIDX:IT&var=640122345949&_trksid=p2060353.m1438.l2649

I'd forgotten about stuff like that, although I have to confess that I was more interested in a home-brew method.

 

[Nomad]

You can either use urine ( ammonia) or hard boiled eggs.
Method 1: wee in a plastic bag
Place throughly cleaned and de fatted brass inside, close, make sure urine covers all brass

Method 2: hardboil a couple of eggs. Let cool, remove egg yolks.
Crush the yolks, cover the throughly cleaned and de fatted brass with the eggyolk paste.
Place in plastic bag, close.

Note: the brass must be as cleas as it can be. Fingerprints ( fat) can leave marks, so wear gloves
,

That sounds a tad busy, especially the cleaning. Bear in mind that the offcut was already tarnished and wasn't cleaned at all.

 

[Nomad]

Maybe not as drastic as this though? Used a ferric chloride solution - it cleaned up reasonably well leaving a 'sensible' level of patina

For the verdigris, quite drastic is what I'm after. Was that dipped in the Ferric Chloride, or suspended over it? So far as I can work out the vinegar and salt idea uses the fumes from the vinegar to carry the Sodium Chloride to the brass, which then reacts and the resulting verdigris is Cupric Chloride. Not sure if the acid has an effect on its own.

So far, my bit of brass that's suspended over vinegar and salt isn't doing too well. I get some verdigris, but it's very unstable - wipes off with a paper towel, leaving darkened brass. I just added a load more salt and dipped the part in the solution before suspending it again.

 

[Janne]

Depends on if you want an even, or a more ‘natural’ oxyde layer.

I work with guns a little bit, and want a perfect finish. The cleaning regime I have there is nuts.

The knife handle parts ( brass, bronze, silver) I am more relaxed about.

Another way is to clean off the varnish, then just wear it. It will oxydize fairly rapidly anyway.

Verdigris does come of easily, but the dark oxides are more stable.
I guess different chrmical compositions, with copper as start.