In making plique a jour jewels, I prefer 18k gold as my choice of metal. But as you have seen other karats of gold can be use as well as, copper, sterling silver and fine silver. All of which except the pure metals, oxide when firing the enamels in place.
To deal with the oxidation you can deplete sterling silver by using sulfuric acid and nitric acid for gold. I use nitric acid to deplete the 18k gold in most cases before enameling. But once in a while it is necessary to do so after enameling in the technique of plique a jour. I have started a list of the enamels that are not affected by the acid. By the way if there is a B in front of the number it is Bovano.
If you are using enamels that do not take well with acids, deplete the gold first in nitric. I heat the nitric in a beaker just to a slight steam, and dip the heated jewel into it and the oxides dissolve quickly. I usually repeat this until the jewel can be heated in the kiln and produce no oxides.
It very very important to wear protection!! Nitric is dangerous. I work outside and wear acid gloves and goggles and a respirator. Also on the table is a fan blowing the fumes away from myself and the studio.
Colors in Nitric
A105B When dipped in nitric acid in a quick bath after enameling it dulls the shine and pits the surface. When fired the dullness get worse.
BOVANO #3 HOLDS UP REAL WELL IN NITRIC ACID.
B 518 This enamel was deteriorating, so I put a few drops of nitric acid in the 518, rinsed well and tested the firing of, with no effects except it harden the enamel.Which makes it a longer fire.
Ninomiya #N3, does not work well when washed with Nirtic before enameling.
B 610 Great
N G 338 Great
NG 302 Great
B 209 Great
L 69
H 24
LT 74
LT 71
LT 70
H 55
N 73
N 72
N 71
One thing I figured out this week when using colors that are affected by the acid is to add a layer of Bovano’s # 3 over the color and all is fine.
Hi Patsy,
Thanks for the information. I carefully wash my enamel, T8 BLYTHE BLOSSOM OPAL WHITE, in distilled water until the water is clear. I still get white specks in the fired surface. This is even with new shipments from the supplier who claims the batch is recent from the manufacture. Have you worked with this enamel and do you know if a nitric acid wash will work on it? Any help is appreciated.
Sam
Hi Sam,
You usually do not wash opals. Rinse once to see it there might be a trash or unwanted particles. Over washing might take away the material that really makes an opal enamel.
You might want to check your kiln.
I do not fire copper in my kiln because there can be tiny black dots, that is oxidation off the copper, flying around in your kiln. If you need to use copper take blow dryer before you turn it on and try to blow out all the groves where the elements are. Even the metal trivets or wire racks oxide and release small particles that can get in you enamel. When you take your hot enamel jewel out of the kln if any land on the surface it will adhere to your enamel.
I had this one time and it made me crazy till I realized the kiln warp was metal coated with paint or a similar coating and the heat escaping from the kiln when opening and closing the door cause the rim around the opening to rust. When opening and closing the door fine particles landed in my enamel.
It was simple to sand and coat the door opening with a rust preventive paint. If the black dots were in you washed enamel you would see them before applying the enamel to your jewel.
Have a great day! Patsy
Hi, Patsy – when you deplete the 18k gold before enameling – what % nitric acid do you use?
Hi Nina,
I use Regents 75% nitric from Art Chemicals. They have posted they are temporarily closed. I this you can kind a local supplier. 550ml is usually $90 but that includes hazardous shipping. I do not dilute it. Save the leftover in an airtight container to reuse till it weakens.
Quick tip, I repeat depletion till I can place it in and out of the kiln as many times as I need in the planned firings of this one jewel. Between each nitric dip, dip in plain water, dry and fire. The metal will be frosty in the end so a light tumble, wipe off tumble residue with hydrogen peroxide.
And have fun enameling!
Nitric acid is very poissonous , corrosive and hard to obtain, so I am using a weak solution ( 15% ) of Clorhidric acid with water . Works excellent with any yellow gold , especially with 18k , leaving a beautiful mate yellow lemon colour and most of all , not damaging the enamel . And not needing warming , the depletion is fast at room temperature , almost 2-3 minutes , maximum .
Of course , not good for silver or copper , but the best for yellow gold .
Thank you for the post. I have not explored Clorhidric Acid, but I will. Like you said nitric is dangerous and takes a lot of precaution.
Patsy
Would you use this on 14K? Patsy Croft
Glacomo,
I can not find that here in the US. Is it possible it could be under a different name?
Patsy
Patsy, Is Hydrochloric acid same as Clorhydric Acid ?
Hi Nina, I have never used or heard of Clorhydric, nore can find any info on it. Where did you see it?