Problem priming copper

[miller]

Happy New Year all.

I am having a problem in priming copper.

I have keyed samples with orbital palm sander 220 grit EVENLY.
http://i179.photobucket.com/albums/w...7/DSCF1301.jpg
I applied liquid garlic as suggested in various literatures EVENLY.* Then I applied Rublev Lead Oil Ground.

First samples tried had quite a thick layer of ground applied. After 24 hours the lead ground dried. However there appeared dark patches at the edges or in the middle. The patches are shaped in blob-like fashion as if lead ground beaded out:
http://i179.photobucket.com/albums/w...7/DSCF1271.jpg
http://i179.photobucket.com/albums/w...7/DSCF1269.jpg


These patches can be wiped clean with finger or cloth within 24 hrs (note rest of lead ground has already dried). If left unwiped, the patches take 2 more days to dry!
http://i179.photobucket.com/albums/w.../DSCF1271a.jpg


Near the patches in the middle some cracks also appeared within 24 hours (a patch in the middle for instance coveres a 1 inch area):
http://i179.photobucket.com/albums/w...7/DSCF1278.jpg


I tried a sample with very thin lead ground (rubbed in with finger/thin gloves like in most literatures) in good north wind weather and I got the same patches within 24 hours. This time, the beading patch was tiny in comparison for the thin layer sample (covering around 1.5cm)
http://i179.photobucket.com/albums/w...7/DSCF1296.jpg


Does anyone know what is happening? Something must be wrong! The patches are not the result of thinner applied ground- there are areas with very thin layer that have dried up normally. These patches take longer to dry and they have strange shapes. I really thought copper would be the panel support for me but din't believe I would find these issues before actually begning anything. I applied lead oil ground on pieces of aluminium plates to make colour charts and i never had these issues. Did them in a jiffy with a telephone card.

rgds

miller


*
Garlic is believed to aid drying in sanded crevices (as suggested by Sapanish A. Palomino 1715 - not proven because a thin ground layer would aid drying more) and possibly provide sticky layer for the primer. Fench Pernety 1757 does not mention garlic. These suggestions are mentioned in essay on technique in "Copper as Canvas" book. A contemporary source lists a chemical reaction that acts against verdigris.http://askmaurice.org/copper.html which is claimed essential for non-peeling of ground.

[ 04. January 2009, 08:06: Message edited by: miller ]

[Kenneth Freed]

Miller,
I would defer to George on this subject but let me ask you two questions.
1) Did you stir up the ground in the can and did there appear to be any separation of elements?
2) Did you do any samples without the use of garlic?

[miller]

Hi Kenneth

1) Did you stir up the ground in the can and did there appear to be any separation of elements?

Yes, I stirred the ground very well in the can before using. I'm not sure what you mean by "did there appear to be any separation of elements?" If it refers to the ground in the can, yes there was separation, but I stirred well.

2) Did you do any samples without the use of garlic?

Yes a very small piece, which was like the first sample had thicker ground (not finger rubbed). The sample showed no patches but it was very small. I just finishes a larger sample without garlic, same sanding procedure and finger rubbing. Will be able to see results in 24 hrs.

[ 04. January 2009, 07:26: Message edited by: miller ]

[Lala]

Hi Miller,
I paint on copper for a long time already and i never had any problems. First of all you have to read that Copper as canvas book carefully. It does not mention huge amounts of garlic juice, it just says rub with garlic clove....

What I do is
1)I take a clove of garlic, I cut it in half and i rub the copper with that clove.
After that i brush off of whatever garlic bits that might have fallen out.
2) I brush lead white with some charcoal and earth (it's kind of off-white greenish, but very light tone), I work it in with a bristle brush to make sure i get into the crevices
Don't use lead ground, use pure lead white.
3) do NOT put thick ground on copper:
it mentions in the book that the ground on most paintings is so thin that you can still see the pink of the copper.

I never had any problems, though so far my oldest paintings on copper are only about 5 years old [img]smile.gif[/img]

Happy New Year!
Lala

[Lala]

Ah, and another thing, I actually press the lead ground all over with my thumb (or fingers), of course it's not mandatory, but it makes the surface so smooth and velvety (made of fingerprints!). You can see such fingerprints in the ground of paintings in the Copper as Canvas book.

as for the garlic, I use it just to get a hint of the juice on without real substance, the only reason i do it is to follow the old recipe - garlic juice is water partly, and water mixing with oil is not a good idea... I think this actually might be the reason for your problems with the ground.

[miller]

Dear Lala

Thank you for your important replies and Happy New year. Yes I use the finger method too- thinner layer the better. May I kindly ask these questions. I appreciate sharing your experiences.

1) Do you/how do you sand the copper? (method used, sandpaper grit etc)

2) When I used half a clove of garlic:

- glove itself turns green

- it gets unevenly applied so when i reapply I get dirty washes from sanding debris. I dry clean the copper many times but still I get sanding debris. These will show through the paint layer and I'm not sure if the washes are "healthy"
http://i179.photobucket.com/albums/w...7/DSCF1198.jpg
The right top part is passed once with garlic. The bottom twice while still wet. Do you get this?


- like you kindly mention, I get garlic debris around the plate and they stain the copper really dark. When I brush them off while wet (so that they dont stain) it removes the garlic layer!


3) Does the copper finally change colour after you apply the garlic?

4) Why pure lead white not oil ground?


Thank you
miller

[ 04. January 2009, 13:39: Message edited by: miller ]

[George O'Hanlon]

What you may be experiencing is residual oil that is most difficult to remove from the surface of the copper plate. A representative of Revere Brass said that it is very difficult to remove all of the oils from copper sheet, and that the sheet will be "oil canned," a term in the industry that indicates a metal sheet that is not truly flat -- you push down on a bubble here, and it pops up over there. The oil causes the most problem with paints and adhesives and add to that the stresses from "oil canning" and you've got more problems. To eliminate most of the oil, degrease it with an aromatic solvent (such as xylene).

Please review other threads in this forum for recommendations on preparing copper panels. I think if you follow these you may be able to eliminate the problems you are experiencing.

[bart johnson]

When I was etching some years ago at a local printmaking shop they had outlawed using any toxic materials. They used Ajax to degrease the copper plates. You might see if that works as an alternative if you want to stay away from fumes.

[miller]

I did a test without garlic and got a couple of patches as well. The dark patches showed within minutes. Overnight they were identical to others described above.

When should Xylene come in - after sanding? Won't that be an additional chemical to react with the copper?

Also, Lala suggested to use pure lead white not oil ground. George (and Lala) what are you opinions on this?

Would resanding the patched area and re-priming be a problem especially if the surrounding ground is touched with garlic or xylene?

[Lala]

Thank you for the oil hint, George! I use rubbing alcohol or even turpentine (i guess best before sanding, I don't know if they work worse than Xylene or no...
The reason i was arguing for lead in oil and not lead ground is because that's what all old recipes say, and i hope those people knew what they were talking about. :D But i guess it's ok to use lead ground, i just don't see why. On your picture by the way, that looks like a lot of garlic juice! Maybe it's just the picture. I just rub it very slightly to get the surface a tiny bit sticky, not at all wet, since I think garlic was used mostly to promote adhesion in the crevices and not to make an oil-garlic "emulsion"... For example Van Dyck (i think) wrote about using onion or garlic to rub the dried part of any painting so that the paint doesn't bead on it, but sticks to the surface.

By the way Miller (or George), I'm curious, what gage or weight (or thickness in mm) of copper do you use?