Author Topic: Vinegar As A Brass Etchant  (Read 816 times)

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BCR751

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Vinegar As A Brass Etchant
« on: September 20, 2016, 01:09:14 PM »
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I read/heard somewhere that vinegar makes a decent etchant for brass prior to painting.  Is this an old wives tale or is there some truth to it?

Doug

wazzou

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Re: Vinegar As A Brass Etchant
« Reply #1 on: September 20, 2016, 02:12:11 PM »
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Truth. 
Plain white vinegar. 
It has been many years, but from memory, you don't want it in for much more than an hour and be sure to rinse it thoroughly as the vinegar will continue to work if not rinsed.
If you are not planning to paint right away, it's important to seal it in something with as little air as possible as the freshly minted shell will oxidize quickly.
Bryan

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thomasjmdavis

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Re: Vinegar As A Brass Etchant
« Reply #2 on: September 20, 2016, 02:23:31 PM »
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The answer is: that depends....

If what you want to do is paint a piece of brass sheet stock, yes, unquestionably (at least in my experience).

If what you want to paint is a $1000 brass locomotive, I am not going to answer the question until my attorney finishes the 6 page disclaimer and liability release. 

Try a quick web search for "vinegar tarnish removal" or something similar to get more ideas than what I present here.  (Following based on my experience, use at your own risk) White vinegar only.  Safer than stronger acids.  Keep a close eye on your parts, don't leave stuff soaking overnight, my experience is something on the order of 5 to 20 minutes.  Rinse, use a soft toothbrush to apply a paste of water and baking soda to neutralize any remaining vinegar.  Rinse again and allow to dry about 3 times longer than you think necessary, prior to painting.

The other caveat is that a lot of brass parts nowadays come with some sort of clear coat, which could, depending on what they used, render the vinegar bath unnecessary (that is, the clear coat takes paint, or at least primer, without any further treatment), OR require removal to make the vinegar bath effective, OR (worst case) the coating turns into some gelatinous mess when soaked in vinegar.
Tom D.

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BCR751

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Re: Vinegar As A Brass Etchant
« Reply #3 on: September 20, 2016, 03:28:32 PM »
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I just have a few small brass detail parts that need to be painted, some from MBE and some from Gold Medal Models.  Nothing very expensive.  I'll give the white vinegar a try.  Sounds like it will do the trick.  Thanks for the suggestion.

Doug

robert3985

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Re: Vinegar As A Brass Etchant
« Reply #4 on: September 22, 2016, 03:49:52 AM »
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I've cast thousands of lost-wax brass parts over the years, and also both built and modified brass structures and rolling stock/engines and I never (NEVER) found it necessary to "etch" any of them to get paint to stick to them. 

The trick is to make sure to get all of the waxes and oils off of the brass part.  I first wash them in a mild, warm, soapy water solution (I like Dawn) brushing them with a soft, clean toothbrush, and then I blow dry them with clean, dry compressed air, holding the mounting pin or sprue in a hemostat so they don't blow away.  Then, still holding the part in a hemostat, I liberally brush them with clean Bestine (Heptane) and that takes about a minute to evaporate.  At this point, they are ready to paint.  I have a lot of hemostats, and I hang the parts attached to the hemostats on my spray booth on hooks I have there for that purpose.  I can hang a dozen hemostats clamped to cleaned parts, painting them one at a time.

I find that enamel based paints work best with brass.  I like Scalecoat II the best.  I apply a thin covering coat of paint to the brass object and let it dry for about ten minutes, then look at it and see if the paint has fully covered everything.  Light colors usually need another coat, whereas blacks, browns, greens and blues cover in one coat.

After making sure there are no pools of wet paint on the brass object, I place them in a pre-heated toaster oven at around 175 to 185 degrees.  I use an oven thermometer to tell me when the oven is ready.  I bake them between 10 and 20 minutes, then remove them, hanging  them again on my spray booth hemostat hooks and let them cool.

This process works GREAT for me, and the paint is always durable and never, ever peels or flakes.

If your newly painted brass object still smells of paint thinner after it's dry, you need to bake it longer.  The paint is cured when the paint thinner odor goes away.

Just sayin'

Cheerio!
Bob Gilmore