Longevity of water-gilded Copper Leaf on glass

[BruceJackson]

I am preparing a report for a client on a sign done in copper leaf and would like your independent comments.

The sign was done using water gilded copper leaf in reverse on glass. The outlines were laid on first in oil-based enamel (one-shot equivalent). The letter infill was then water gilded in copper leaf with gelatin water size made up slightly stronger than for gold leaf work. It was subsequently backed up with oil-based backing paint followed by a coat of clear oil-based varnish.

The sign is located in a café in an air-conditioned building in a coastal sub-tropical location.

The copper was bright salmon pink (typical of new copper) when it was done in mid 2005. It has now darkened slightly and is developing a patina of other color.

I would like some comments from people experienced in using copper leaf in this way, especially if you have seen this occur before. Please include comments that respond to the clients concerns of:

What is causing it?
Would this normally be expected to occur; and if so, within what timeframe?
What will be the long term result and how long will the sign last before needing to be replaced?


Original photo taken in June 2005


Recent photos

[DAVE SMITH]

Hi Bruce

I have never used copper leaf for water gilding before only to acheive a matt finish using oilsize. What size were the sheets of copper used for the job Bruce? Schlag leaf ( dutch metal leaf)which is an alloy of copper and zinc is available in copper red and yellow is this what was used? The sheets are alot thicker than normal goldleaf. Schlag is used for more temporary effects like scenery work etc. There are leafs on the market now with a slight copper colour to them which you may won't to try .I 'm not exactly sure what is causing your problem mate .
Sorry not to be of much help just things to consider, someone must have done simalar work here.
Dave

[Sarah King]

Hi Bruce,

I think your main problem is using oil based enamel next to the copper - in the outlines and in the backing paint. Using this kind of paint next to real gold leaf is not a problem because gold is the only non-reactive metal. It never tarnishes. Copper tarnishes easily and is probably reacting to the pigments in the paint. Even trace amounts of sulfur, for instance, will continue to react with the copper long after the sign is dry. As we all know, paint ages and changes even after all the solvents have evaporated. If you have to redo the sign, you might want to seal the copper areas with a tarnish inhibiting clear varnish such as Permalac or Syncrylac before you paint in the colors.

Having an "antique" sign is great when it happens on purpose - not so great when all those little molecules decide to get together on their own.

[Mike Jackson]

Hi Bruce,
I never tried water gilding copper leaf either, though we have some books of it here. Worse yet, I don't have any suggestions or solutions to offer. I've seen copper varigated leaf last a long time when held to the glass with varnish, though I suppose it would be possible to get some discoloration of the copper if the oil size has sulphur in it. I think we used ww window spar, but also some One-Shot quick size on occasions.

Good luck on it if you go at it again. You have as much experience with this stuff as anyone here, so we may not be able to solve the problem or give too much insight. Nice job, even if the copper failed on you!

Mike Jackson

[Roderick Treece]

Bruce,
My first thought might be the water or geletin you used when guilding the copper.
Because I'm seeing patina happening through out the lettering vurses just on the sided where it might be affected by the outline.Copper leaf is too thick to patina through the back so I don't think it's the backing paint.
I've done alot of work with copper metal and copper leaf and I can't remember a time when leaf or metal tarnished with any type of paint or clear over it.
I happen to think it looks pretty cool with the patina.

Good luck
Roderick
www.goldleafsigns.com

[Doug Bernhardt]

My first reaction.....is Sarah has the right idea. When I approached Rick "the Boss" Glawson about this idea quite a few years ago ,his reply was "why bother?" and offered up a gold leaf with almost the same colours. He was of course right as the leaf...(still have some at the shop and will try and remember what it's called) (long quotations) was the same in colour without the negative reactions you descibe and show. I gotta say though...that must have been some strong size you mixed!!

[Mike Jackson]

Doug, are you thinking about "moon gold"? Or maybe "rouge gold"?
https://handletteringforum.com/forum ... =moon+gold

We had some discussion on them earlier, seen in the link above.

Mike

[BruceJackson]

Moon gold is actually more like platinum in color. A warm grey. When compared with other white metals it is darker and browner. It's beautiful.
The one I get is a high carat gold, usually over 23ct with a touch of palladium. Just a little palladium goes a long way to change the gold's color.

Doug: the size was strong, but not ridiculously strong. The main issue with copper, being thick, is its difficulty in cleaning off excess metal. In this case, with the double outline laid on first, I could tear away the excess beyond the outline while the size was still damp. One sheet per number with no laps. I learnt through bitter experience years ago that cleaning off dried excess leaf the usual way, requires a strong double backup and a scourer!

----------

Thanks for the comments. I have to say, they haven't quite addressed the situation as I expected.

The client specified water gilded copper leaf.

My contention is that copper will always change over time. Even using clear coats and backing paints doesn't completely inhibit the transmission of moisture and oxygen. They are effective in slowing down the ageing process, but they are still permeable. Copper, being highly reactive, will still change color. Shellac and similar synthetic thermo-plastics are less permeable than oil/alkyd resin, but none will provide a perfect seal in my opinion.

Every thing I've ever done work in copper leaf, whether oil or water gilded, glass or surface, it still changes over the years. It goes from fresh pink to orange, then to variegated colors and brown. It fiinally develops verdigris if exposed for long enough.

Incidentally, being pedantic: tarnishing is what happens to silver in the presence of sulphur. Oxidation is what happens to other metals going through a chemical change as they take up oxygen.

[Dan Seese]

A couple of years ago while out at Larry White’s Dead Man event I did a Dickinson’s Metal Works project and, utilizing Sarah King’s expertise, did an “angel gildâ€￾ using the copper mirroring solution for the main lettering.
https://handletteringforum.com/forum ... php?t=1327
Over time, the lettering began to take on a blue hue. It looked pretty cool, if I could just arrest it. Unfortunately the patina (thanks, Bruce, for your pedantry) has continued and a lot of the areas are now black.
What I’ve noticed is that some of the lettering is totally unaffected. I had done the background simulating various metal plates, in keeping with the “metal worksâ€￾ theme. Some of the plates were done using aluminum bronzing powder. Others were done using aluminum leaf. Then I backed everything up using Fine Gold backup or One Shot (I don’t remember!)
Anyway, the areas where the aluminum leaf overlapped behind the copper lettering is where the copper color has remained unaltered. I suppose the thick aluminum leaf created some type of barrier. I’m no chemist so I don’t know the related science but this is simply my observation. I also realize I’m talking about a copper solution as opposed to copper leaf so maybe it’s a completely different problem. However, similar to water gilding, the copper is held to the glass with a solution and gives a mirror finish as opposed to being held to the glass with an oil size or a varnish and giving a matte finish.

[Danny Baronian]

Hi Bruce,

I think what's happening is oxidation. As well as the back up might be, I think air will eventually get in through the edges.

A while back we completed a job for a client that included window lettering with flash gilded copper mica onto size, no problems there. They later wanted a quantity of double doors with designs gilded with bright copper showing on both sides.

A sample was made by masking the image, sized by spraying on Wunda size, laying the leaf, and backing up with epoxy screen printing ink. Worked and looked fine up to that point. After two weeks out doors at their office in Tahoe - to accelerate any possible problems, the edges began to show veins of darkening, beginning at the outside toward the center, and continued to oxidize.

Sun exposure, heat, humidity and sudden, drastic temperature changes would most likely shorten the life span of any product, most of which were present in the area.

A second sample was made with two pieces of glass, 1 with a positive image, the other a mirror image of the first. The two were assembled as a dual pane window, and looked fine at one angle only. From any other angle, the rear image was visible and looked bad. End of project.

During the process, I talked with Jennifer at Sepp leaf where the copper was purchased. According to her, she knew of nothing that would prevent the copper from oxidizing. From those they supplied to, including pin stripers using it on vehicles, experienced the same problems with copper.

If you have any questions, give her a call, as she was very knowledgeable and helpful.

I aggree with Rod on the patina, but Rod was probably not the client paying for the job.

Danny

[Roderick Treece]

Good morning Bruce,

I started a test yesterday to see what would happen if I put a peice of copper leaf on glass useing just tap water.
Plane water was sprayied on the glass and then I layied the leaf on the glass.I put more water on top of the leaf.

After about an hour I was getting some pretty cool patina going.The back of the leaf had more tarnishing than the front and it had defferent colors as well.

Images on following post.

Thanks to Danny for posting the photos

Roderick
www.goldleafsign.com

Edited by Danny to add photos on following post

[Mike Jackson]

Front:



Back:



I am not sure why Roderick's copper leaf image doesn't want to show up in his post, but it works in this reply.

Mike Jackson