How long will Multi-Etch last?
For dry powder: at least 11 years.
For unused Multi-Etch in solution: at least 6 months (keep it capped!)
How much titanium or niobium will one gallon of Multi-Etch etch?
Approximately 1,500 square inches of titanium when dipped for three seconds at 120-150oF. As you etch, the etchant gradually becomes ineffective/neutral.
Can I restore the effectiveness of Multi-Etch after it has been used?
No, that’s why it’s best to use only as much as you need in any one sitting, leaving the rest unadulterated.
How long should I etch to remove anodizing mistakes?
If you simply went past your target color, you can dip the piece briefly in Multi-Etch and it will work backward through the colors. Be sure to rinse as soon as you see the color you want.
If the color is uneven and you want to start over, etch time will be longer than when you etched the raw metal. Just keep etching until the color disappears.
What should I use to hold the piece I am etching?
We use titanium or niobium wire bent around the piece to be anodized, or strung through a hole in the piece. You can also make a plastic holder by drilling holes in a plastic medicine bottle. Affix a handle if you want or suspend the holder from a wire made of titanium or niobium.
I’m not getting any color on my etched titanium.
If there isn’t any change in color, check your connections. After using many techniques to anodize over the last 35+ years, sometimes we still get our wires crossed!
Why is the anodized color on my titanium pieces splotchy in places?
This is the most common question. There are many variables to consider, described below.
What alloy and form of titanium are you using?
Our experience is mostly with grades 1 and 2 “commercially pure” titanium sheet and wire. Sometimes the ends of a batch of wire or sheet have a heat oxide that is very hard to remove. You also can’t see it! But if you suspect that might be the problem because most of the pieces in a batch anodize fine, try etching the “bad” pieces longer and avoid using the high-voltage colors if possible. The aircraft grade — 6/4 — usually colors well without any etching at all.
Cast titanium parts like medical implants sometimes have a whitish alpha-case from heat which must be mechanically removed (e.g., sand-blasting) If this is not removed, it may be difficult or impossible to anodize evenly with higher voltage colors. Try etching longer before anodizing.
Make sure you have degreased the metal before etching.
If the metal is really dirty, e.g., after tumbling, etch once, rinse well, and etch again. Hold the pieces by the edges so that you don’t leave fingerprints.
Did you accidentally contaminate your etching bath?!
If you introduce brass, copper or iron into the etching bath, those materials will tend to plate onto the titanium and interfere with anodizing. If that happens, you will need to throw out your contaminated etching bath and start with a fresh one. These contaminants could come from the tooling you use to form your piece–files, saws, etc. If possible, keep a separate set of tools or clean the piece with an ultrasonic before etching.
Grow the oxide slowly.
If you’re aiming for the color at 70 volts, start at 60 and, while leaving the piece in your anodizing bath, keep the voltage at 60 and see if the color continues to advance to the higher voltage color. If it doesn’t, try increasing the voltage slowly.
Make sure you rinse well after etching the metal.
If you drag Multi-Etch into your anodizing bath, it can inhibit good color. If you are not going to anodize immediately after etching, protect the clean surface by applying a 10-volt color. If you don’t want to anodize at all, then store the etched pieces in distilled water. This will allow you to wait months if necessary, before anodizing.
What are you holding the titanium with while anodizing?
Using something other than titanium or niobium as hanging/holding wires when anodizing can prevent the voltage getting to the titanium. Some metals, such as copper, brass, gold, etc. will draw off the voltage. Some people use a plastic container with a titanium or niobium probe to anodize–this works great for anodizing lots of little pieces.
What is your anodizing solution?
We use 1 tablespoon of ammonium sulfate per gallon of distilled water. You can get ammonium sulfate wherever gardening supplies are sold.
Reactive Metals Studio recommends using TSP. Start with 1/8 cup per gallon of distilled water. If the anodizing reaction is too slow, add a little more TSP. For a bath of either ammonium sulfate or TSP, you can squirt a little dish detergent or Simple Green to act as a surfactant, which is important when you are after a smooth gradation from one color to another. Without that, sometimes the liquid “beads up” when lifting the titanium out of the bath.
It’s possible that if you purchased distilled water in a plastic jug that has been sitting around the store awhile, the water may have absorbed something from the plastic jug itself. Try using water from one of those purified water vending machines.
DO NOT ANODIZE WITH Multi-Etch, sulfuric acid, or detergents with fancy spot retardants.
When mixing Multi-Etch, double strength for cold etching, allow at least 24 hours to completely dissolve the Multi-Etch powder. Shaking the container before use can also help.
Sometimes everything is “correct” but you still can’t get even color in the higher voltages. This is not because of the etchant but is due to inconsistencies on the metal itself. High-voltage colors are the hardest colors to achieve so if you have a choice, choose a lower voltage color, especially for the problem pieces.
If you discover something not covered here, please let us know! firstname.lastname@example.org