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How to restore finish on turn of century black cast iron drafting table base

I have an antique drafting table with a cast iron base. The original finish is black. In many places, it is rusted through to the bare metal. How can I restore the original finish? Thanks for any help.

Brent Williams
Hobbyist - Dallas, Texas
April 5, 2008

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First of two simultaneous responses -- May 2, 2008

We have no way to know what the black finish was originally. If paint, then wire brush, prime and paint.

It could have been oiled with a drying oil (such as linseed), it could have been rubbed with graphite, it could have aged naturally to black.

Jeffrey Holmes, CEF
Spartanburg, South Carolina

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Second of two simultaneous responses --

You can remove rust with 5 % ammonium citrate solution(50 gm citric acid ⇦this on eBay or Amazon [affil links] /1 lit water+some ammonia,pH must be 3,5).If you want to use old style technology try 20 % shellac and some black pigment or you can use Hammerite Rust Cap [affil links] paints. You must remove old paint (with paint stripper or hot air gun).Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
May 5, 2008

Before painting you can use 20 gm tannic acid ⇦this on eBay or Amazon [affil links] /15 ml phosphoric acid/1 lit water solution-simple do it yourself rust converter ⇦this on eBay or Amazon [affil links] .Instead that you can use very strong tea or oak bark(or chestnut or any astringent tasted plant)decoction.Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
May 9, 2008