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Resist peels off during etching


#1

I am etching silver in nitric acid. My problem is that sometimes the
asphaltum or nail polish I use to resist the etch peels off. What to
do?

Yvonne


#2

Yvonne, Possibly the nitric acid is too strong. You might try a
weaker mix. If diluting, remember to add the acid to the water, or
you will create a nasty explosion of the stuff.

Alma


#3

I can understand nail polish peeling off but asphaltum? the type I
have used would never peel as it doesn’t really dry it just gets more
and more viscous. But in either case you very likely are not getting
the metal totally clean and the resist is not developing good
adhesion to the metal.

James Binnion
James Binnion Metal Arts


#4

don’t use nitric acid – It will start to damage the resist edges
quickly. use ferric nitrate or electroetching. look at the archives
( saves me time) or I will send you a list of places that can help.

just ask.
jesse


#5
I am etching silver in nitric acid. My problem is that sometimes
the asphaltum or nail polish I use to resist the etch peels off.
What to do? 

I find that it helps a great deal to pre-etch the silver for one
minute before applying resist. Do not touch the surface after
etching-- rinse thoroughly, pat dry, apply resist. The "tooth"
created by etching seems to help keep the resist on.

Noel


#6

I know that you can use ferric chloride to etch copper, brass and I
believe bronze, but that it will not etch sterling silver.

Can someone verify this?

Thanks
Debbie


#7
I know that you can use ferric chloride to etch copper, brass and
I believe bronze, but that it will not etch sterling silver. 

Debbie, for etching silver, you need Ferric Nitrate.


#8
I know that you can use ferric chloride to etch copper, brass and
I believe bronze, but that it will not etch sterling silver. 

You do not want to use chlorides to do anything with silver. They
form an insoluble salt-- You can etch sort of but the etch will clog
up with a white solid.

jesse


#9
I know that you can use ferric chloride to etch copper, brass and
I believe bronze, but that it will not etch sterling silver. Can
someone verify this? 

That is correct. Just as hydrochloric acid doesn’t etch silver, it’s
salts, such as ferric chloride, also won’t etch silver. The reason is
that the product of silver and hydrochloric acid reacting, is silver
chloride, which happens to be insoluable in water. So when exposed to
the acid, or the chloride salt solution, the surface of the silver
reacts, forming silver chloride, but that product then does not
dissolve, but instead remains a surface layer, which then stops
further etching. So hydrochloric acid, or ferric chloride, will
damage the surface of the silver, giving it a rather dingy look (that
some people use as a form of aged patina) but they won’t etch beyond
that surface effect.

Instead, use ferric nitrate, a nitric acid salt. Or nitric acid
itself, diluted, of course. These work because silver nitrate, unlike
silver chloride, is water soluable.

A further, and sometimes useful, demonstration of the difference is
that you can use the insoluable nature of silver chloride to recover
the dissolved silver in your nitric acid or ferric nitrate solution.
Add ordinary table salt to the used etchant, and it reacts with the
silver nitrate to form silver chloride, which then precipitates out,
and the white powdered silver chloride can be filtered from the
solution. The silver chloride can then be sold to your refiner (not
all of them take it, though), or with additional steps, it can be
reduced back to silver. Of course, you can also recover the silver
from your nitrate solution by electroplating it out, once excess
acid has been neutralized, which might be simpler, should you be
bothering to try and recover the dissolved silver at all…

Peter Rowe


#10
I find that it helps a great deal to pre-etch the silver for one
minute before applying resist. Do not touch the surface after
etching-- rinse thoroughly, pat dry, apply resist. The "tooth"
created by etching seems to help keep the resist on. 

Not only that, but you’re removing a microscopic layer of metal, and
any contaminants on the surface goes with it. Super cleaning. We did
that for circuit boards. The copperclad was dipped in a "bright dip"
which was a mild etchant, then triple-rinsed in distilled water
before the resist was applied.

Al Balmer
Sun City, AZ


#11
I know that you can use ferric chloride to etch copper, brass and
I believe bronze, but that it will not etch sterling silver. Can
someone verify this? 

You are correct about the silver. I’m not sure if FC will etch
bronze, but since it’s mostly copper, maybe it will.

You can buy FC buy the gallon from Graphic Chemical and Ink in
Illinois. And lots of us here on Orchid, including me, like PnP
paper, (Press 'n Peel) for the resist.

Elaine
http://www.CreativeTextureTools.com


#12

If your nitric is diluted properly, check to see how old your
asphaltum is.

From what I have experienced old asphaltum can lift easily. Using
fresh asphaltum will take care of the problem.


#13
Of course, you can also recover the silver from your nitrate
solution by electroplating it out, once excess acid has been
neutralized, 

If the silver is fully dissolved, as in silver nitrate, you can
simply place a piece of coiled pure copper wire (thick wire is
better) in the nitrate solution. The copper displaces the silver
from the solution to give copper nitrate solution and pure silver
metal. It’s quite fun to watch the pure silver “grow” like fur on the
copper wire. It is easily shaken off and collected, just by filtering
and washing. Keep doing it, making sure the surface of the copper is
clean, until no more silver will come out of solution.

Helen
UK