Aluminum etching

A. Acid anodizes aluminum (forms aluminum oxide adsorbed on the surface). It is often faster to etch aluminum using caustic soda (NaOH). At least based on my experience.

A. 10% Nitric acid, 1% Hydrofluoric acid, and 89% Distilled water should do it :)

A. I'm using ferric chloride (FeCl3) to etch aluminum right now with pretty good results. I got it from a PCB etching kit from Radio Shack. Mike N - Auburn, New Hampshire ++++++ A. Quick cover in NaOH, then etch with HCl Jake W - Frankfurt, New Mexico

A. 50% caustic soda solution with water will do a very good etching for aluminum. the free caustic soda conc. should be 10 oz/gal.

A. Try Spiderspit. This is a guy in Texas that has a product that is specific for etching aluminum. I just did a search and couldn't find it but I know it is called Spiderspit.

A. For etching on Aluminium try these formulations --
1) Distilled water 380 ml, +HNO₃ 10 ml, +HCl 6 ml, +HF 4 ml.
(Caution-except distilled water all the rest of the chemicals are corrosive acids. Always add acids to water and not water to acid.

2) Distilled water 200 ml, +ferric chloride 10 gms., +hydrochloric acid (HCl) 100 mls

3) Phosphoric acid---80%
Acetic acid -- 5%
Nitric acid -- 5%
Distilled water -- 10%

4)Copper sulphate-- 10 gm (CuSO₄)
Sodium chloride ---5 gm
Distilled water -- 100 ml.
Take care while handling. use rubber protective gloves

A. I haven't tried the approach explained in homepage.usask.ca/~nis715/salt.html but I read the article in detail, and it should work as explained:

The solution used there is:
CuSO₄ (copper sulfate -- bluestone) 1 kilogram
NaCl (sodium chloride -- table salt) 250 grams
NaHSO₄ (sodium bisulfate -- Sani Flush ) 25 grams
H₂0 (water) - depending on bath strength 10-20 liters

This can be compounded dry and water added to use. It contains far fewer dangerous components than other mixes I have seen. Advice is given for replenishing the solution, and disposal is bio-friendly and safe for drains.

The process takes advantage of the electronegativities of copper and aluminum (or zinc) to create a replacement reaction which removes the aluminum. All of the materials can be obtained easily and cheaply.

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Ed. note -- Unfortunately, the referenced URL no longer exists.
Readers: when possible, please try to include an article name, author, or other clues to find an article when referencing it because web links often break within a very short time.

A. I had the privilege of studying printmaking at the University of Saskatchewan (some 10 years ago, 4-yr BFA) while Nik Semenoff (author of above recipe) was the artist in residence there. While I studied mostly in waterless lithography and serigraphy, I have printed at least a half dozen editions using the aluminum etching technique described above. I can verify that it works exceptionally well! Nik's email address is included in the above paper (not sure if it's still valid), but if you experience problems I would encourage you to contact him. The man is a genius.

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Ed. note: Thanks for the author's name, Jon, with which we have been able to find his new website/blog at www.ndiprintmaking.ca/

So pleased to find Larry Stark's recipe in plain English! I lost my recipe. It works well to agitate the etch lightly with a feather while the aluminum is in the etch.

A. I have read through this website and have seen that some printmakers use hydrofluoric acid (HF) and sulphuric acid (H2SO4 as part of the mordant brew to etch Al, Zn and Cu plates. DO NOT ON ANY ACCOUNT EVER USE HF which is so corrosive that it will dissolve GLASS. And there really isn't any need to use the extremely dangerous sulphuric (far more dangerous than other common mineral acids) either - there are plenty of other options.

Copper sulphate/salt are useful for safe etching and ferric chloride is also fine and not that dangerous. Be sensible when handling chemicals and you'll be all right. But for heaven's sake steer well clear of HF, which can do untold damage in the hands of a non-chemist.

Careful when using ferric chloride to etch Al - it might explode in your face, so do tests outdoors to start with. Excellent for spit biting! Caustic soda ditto.

A. Hi, Ger.

Caustic soda will certainly etch aluminum. In fact, it is widely used to completely dissolve aluminum. But I would suggest getting some experience in using it to etch aluminum with maskants or silk screening, to acquire a good feel for reaction rates, quantities, reaction products, etc., before trying to use it in a printer. Good luck.

Regards,

Ted Mooney, P.E. RET finishing.com Brick, New Jersey