Chris Boothe, developer of Multi-Etch
I originally perfected Multi-Etch for titanium production. It’s a nonacid (pH 6.8) alternative to hydrofluoric acid. I’ve also tested it on other metals with great results.
Multi-Etch can be used on the following metals:
- Titanium
- Niobium
- Platinum
- Copper
- Nickel
- Brass
- Steel
- Silver
- Mokumé
- Meteorite
On titanium and niobium, I use Multi-Etch to remove anodizing mistakes and to clean off contamination—iron from rolling mills, heat oxides, etc. Multi-Etch will maintain the finish on titanium and niobium as long as the metal is not etched too long. Here’s a single piece of titanium that I left “as is” on the top, cleaned with Multi-Etch on the bottom, and then anodized. It looks like I anodized them separately but I did it all at once.
Anodized titanium unetched (top), and treated with Multi-Etch (bottom)
Copper and brass etch more quickly than titanium. You can use Multi-Etch to remove light firescale from silver but not from gold. You can clean iron contamination from platinum without removing any platinum ions. I’ve done limited testing with Multi-Etch on platinum for etch effects—that is, removal of platinum ions—and there doesn’t seem to be any effect. I have not tested it with rhodium plating but I assume there would be no effect on that either. Although Multi-Etch will etch glass, it does so too slowly to be practical for decorative etching.
I have used Multi-Etch to remove broken steel drill bits trapped in titanium and gold.
Multi-Etch will enhance the patterns in mokumé and the crystals in meteorites by etching the different metals at different rates, thus slightly raising one over another.
Here is some meteorite showing before and after treatment with Multi-Etch:
Untreated meteorite
Meteorite treated with Multi-Etch
Although my experience is with jewelry, there are many other industries where Muti-Etch is used, such as the medical industry which uses a lot of titanium.
How much to use and how long to etch will, of course, vary depending on what metal you use and what effect you’re after. Below are two examples.
Multi-Etch solution is crystal clear — it looks like water! All containers that are used to hold Multi-Etch should be marked as poison. Dispense into plastic containers marked as poison.
Do not store in glass containers! Provide positive ventilation, eye and skin protection!
Set-Up
The equipment I use is available everywhere: the standard off-the-shelf Pyrex measuring cup and single coil hot plate with a heat diffuser (don’t place the cup directly on the hot plate.) Do this under a fume hood or outside.
Example 1: For a production run of two dozen pairs of titanium earrings, I use one cup of Multi-Etch in a two-cup Pyrex container, heated to about 150° F. You can use a thermometer or look for the built in Multi-Etch bubbles which tell you when it’s ready to use (visual check.) These tiny bubbles appear when the Multi-Etch is brought up to the correct temperature. I dangle a pair of earrings from a niobium wire into the Multi-Etch for 3 to 10 seconds and then rinse in distilled water. If I did three production runs a week, I would change the Pyrex cup about every three months. If you wait too long, the cup can shatter and make a mess.
Example 2: I manufacture a line of titanium wedding rings with platinum inlays. As all platinum fabricators are aware, the accepted method to remove cross-contamination prior to welding or soldering is a 15 minute soak in nitric acid or bisodium sulfate. With Multi-Etch, a 15-second dip is sufficient to eliminate all impurities that could interfere with a perfect weld or solder joint. I dangle the platinum from a niobium wire into the Multi-Etch for 15 seconds and then rinse in distilled water. It’s now ready for a perfect weld.
Instructions for working with Multi-Etch (PDF) from Reactive Metals Studio.
This is a cold process that usually produces beautiful colors on titanium. Try it — if it doesn’t work for you, add the rest of the water and follow the normal instructions above.
Multi-Etch solution is crystal clear — it looks like water! All containers that are used to hold Multi-Etch should be marked as poison. Dispense into plastic containers marked as poison.
Do not store in glass containers! Provide positive ventilation, eye and skin protection!
Cold-Working Instructions
- Add one half gallon (8 cups or 1.89L) of water to the standard one gallon jug of Multi-Etch.
- Mix to dissolve. This may take a little while or let it stand overnight. It should all dissolve. Mark the jug so you don’t mix it up with regular-strength Multi-Etch.
- For best results, the titanium should be clean and oil free. Simple Green® works great. Suspend on a niobium wire — it will last much longer than titanium. The piece can also stand in the bottom of the container. Do not lay it down unless you plan to stay with it and brush the bubbles off.
- Although it seems to work well sitting still, the addition of a little vibration or stirring is a good idea. You can use a little aquarium air pump or even one of the new vibrating razors to add some energy to the process. A magnetic stirrer is excellent.
- Titanium grades 1 and 2 have tested well at 3–4 minutes at room temperature. Test your metals before you commit to the process.
- Rinse, wash of any smut and anodize immediately.
After Etching
Titanium can be rinsed and held in distilled water until you are ready to anodize. Titanium can also be anodized to a low voltage (5–10 volts) rinsed, dried and held to be anodized later at higher voltages. This method locks the surface against air contamination and 3 to 6 months between voltage applications are possible.
Just how safe is Multi-Etch compared to hydrofluoric or nitric acid? Well, while I would never recommend this, I have reached my hand into 100°+ F heated Multi-Etch to retrieve a part and I suffered no ill effects (all ten digits and skin intact).
Download the Multi-Etch Material Safety Data Sheet (PDF). For 24-hour emergency assistance, call (800) 451-8346.
Why did I pursue an alternative to hydrofluoric acid?
In these modern times, dying for your art is just plain stupid. Although in my youth I had my share of unfortunate experience—exploding kick presses, dense orange clouds of acid gas, and even getting shot in a hold-up of my jewelry store—as an artisan-jeweler-metalsmith with close to forty years of experience, my goal is not to die in an industrial accident, but rather, of old age.
Artists courting the muse with hydrofluoric acid need to realize the dire peril involved. Do you really want to find out years from now that your fume hood had back draft, releasing acid fumes into your studio?
I etched titanium for ten years with hydrofluoric acid but I used a full face mask with a separate air supply and a powerful fume hood. Additionally, I took air quality samples with a Draeger tube. These are gas analyzers which read in parts per billion. Yet, even with all these safety precautions, the risk was still too high. Here is one report on the seriousness of exposure to hydrofluoric acid (PDF).
Multi-Etch is available exclusively through Reactive Metals Studio, PO Box 890, Clarkdale, AZ 86324.
Contact them here:
info@reactivemetals.com
(800) 876-3434 or (928) 634-3434
www.reactivemetals.com
I am always eager to learn more about what Multi-Etch can and cannot do. Please email me with comments, complaints, or kudos: info@multietch.com.
—Chris Boothe, developer, Multi-Etch
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