Black or Gray Titanium

March 4, 2011

John Asks:

I’m trying to get a black or dark gray finish on the face of a titanium driver head. What voltage achieves that color?

Sorry, John. Anodizing produces a particular spectrum of colors limited by the first two octaves of optical interference. I explain it here.

Black and gray are shades, not colors. One cannot make titanium black by anodizing.

So, how is black titanium made? Everyone who does it is keeping the actual process a tight secret. But my  educated guess is that it is produced by implanting nitrogen into the titanium using an industrial vacuum effusion furnace. This produces a relatively thick layer of titanium nitride in a similar chemical manner that titanium dioxide is made by anodizing. But nitrogen implanting cannot be done in an oxygen rich environment, like air or water. Air is 21% oxygen by volume, and water is 33% oxygen by atoms, or 88% by weight.


Programmable Voltage Supply?

December 19, 2010

John asked:

Is there any value in a programmable(manual or C/C++) power supply for anodizing?

Say Vout=20+(110*N/(255)); // N=0,1,2,3,4,…255

Giving {20,20.4, 20.8,21.2…129.6, 130}

I can also make this power limited to approximately 13W(0.10A at 130VDC)

I am not selling anything! I am just wondering if this is a worth while adventure.

As a fellow electrical and programming geek, I see the appeal of the project. But practically speaking in terms of anodizing titanium, no. The color is determined by the final voltage, and the faster you get there, the better.

Also, I use down to 8 volts on occasion. And the lower voltages are more color sensitive than the higher, so it should either be 16 bit linear, or have exponential or quadratic output, as in

vOut = (((N/64)^2 + N) *120/255) + 5 // N={0…255}

But if you were to rig an x-y table to such a supply, one could then “print” in anodized colors. However, there is a limited palette. And also one would have trouble with certain adjacent colors, and have to adjust the lateral speed to be proportional to voltage, and maybe fluid flow through the dielectric cathode, and several other engineering considerations.

As such, it becomes fun and useful. But a lot more work. Then you would be able to share it on HackADay.com or Makezine.tv or some such.

In order to make such a project marketable, one would have to write the CADD end to prevent unfulfillable designs. Artists have to have limits imposed.


Is TSP/90 as Good as TSP for Anodizing?

December 13, 2010
TSP90
TSP 

James asked, “Will the TSP/90 Phosphate Free products work as well as the standard TSP brands?”

An excellent question. My first impulse is, “I doubt it.” But I am not sure. The folks at ReactiveMetals.com might have some insight (that I would share here if passed along).

TSP/90 is made with Sodium metasilicate and pentahydrate. So it is an alkali electrolyte with plenty of oxygen carriers in it. So far, so good. But as a cleanser it appears to suffer from leaving behind a film; a bad sign.

If you are concerned about the potential harm of artificial phosphates in the environment, anodizing is not a significant supply. I have been using the same 8 oz. box of actual TSP for the last dozen years. That’s equivalent to a few weeks of laundry. The same batch of electrolyte can keep on going for months, by adding distilled water (the part that is used up) and an occasional pinch of TSP crystals (to keep up the concentration from the drops removed by pulling out pieces). Occasionally, I filter out the dust and bring it to a boil to make sure it stays sterile.

If you want to be even more environmentally correct, use ammonium phosphate (lawn fertilizer) and then dispose of your old electrolyte by spraying it on your lawn. I used a box of this through the 1980’s and 1990’s.

One of these days, I’ll probably expound why the lingering phosphate meme of the 1970’s was somewhat misguided in the first place.


Q: Can I Stamp and Rivet with Titanium?

December 3, 2010

Kelley asks:

I make stamped jewelry and I have never worked with titanium before. Can titanium be stamped with a usual tool hardened steel stamp set? A client is wanting inspirational words stamped on a premade titanium bracelet.
Another question, would my usual method using a riveting hammer and a bench block do with titanium wire to create a rivet?

The short and qualified answer is, “Yes”.

Odds are that you are working with one of the less hard alloys or grades. Titanium behaves much like stainless steel, in that it takes more force to work it than do silver and other “normal” jewelry materials. Hit harder, maybe with a bigger hammer or mallet than you use to mark silver. I use normal steel stamps, myself  (as in this picture).

Where titanium gets its tough reputation from is that it is harder than steel under pressure. Stamps and especially cutting tools wear out faster because titanium, unlike steel, doesn’t get softer at a mere few thousand psi. Silver, gold, etc are softer to start with. I used a 20 oz. hammer to strike this stamp.

I have also used titanium wire to make rivets, using an ordinary little chasing hammer to set them. Nice, soft Grade #1 wire. Here is a List of Grades and their relative hardnesses.


Fusion Welding

March 28, 2008
I’ve been interested in learning how to fusion weld, for a long time, but the Sparkie is so expensive. Does anyone know of a fusion welder that would be less expensive, or even an experienced fusion welder who would provide welding services for a fee?Also, would it be possible to create a “nib” of our own for welding purposes, or do the dimensions (etc.) of the nib have to be exact to get a good solid weld?

Thanks for any help.

-Maggie


How can I get consistent colors?

March 26, 2008

This frustrated email arrived today:

I live in Belgium (Europe) and have been making titanium jewellery for 4 or 5 years now. Sometimes I colour the pieces. I have a machine from Wieland, a German company. All this time I did not have any problems because the pieces I made had always the same size. Now lately we are doing titanium leaves in various sizes; Grade 2 thickness 0.5 mm. The problem with coloring these pieces is that I do not seem to have any control over the colours due to the variable sizes of the pieces. Is there a way to make a formula that gives me control (more or less) by taking the weight of the piece? Because of the irregular shape it is impossible to know the amount of surface I am working with.

At the moment I am really taking what comes out of the machine. I did make several colour charts using various shapes but with pieces 6 to7 times as big as my trials I have no control .

I would be very grateful if you have some advise on this, or maybe even a solution.

Thanks in advance.

Peter

My reply: I can’t know exactly what the problem is, for I encounter the same difficulties.
The color you end up with is a function of the electrical current density, the total time, the surface finish, and the grade/alloy (which also affects finish and current flow).

The weight is not as good an indicator as the surface area. If all the pieces are always the same thickness, then the two are functionally interchangeable. But the risk is that if you calibrate on weight, and then start working with other thicknesses, the calibration will not stand.

I passed the question on to Bill Seeley.


How can I build an anodizer for UK Current?

March 22, 2008

Another reader question:

I am thinking of making an anodizer based on your anodizer digram. I live in the UK but was thinking that the volts for your electricity is different from the UK’s 240 volts?
If so do you know any diagrams that can help me with this, what I need to change?
My first thought is: In the UK, you can use the same Variac circuit. I wouldn’t trust the dimmer circuit because of the instability at lower voltages.
The U.S. uses 110 vac (150 volt peak), so we use about 3/4 of the range of the variable transformer (less if it is wired to provide over-voltage).
In the U.K, you would just just use 3/8 or even half of the available range.

If you really want to use the inferior dimmer-switch design, you can probably find a simple step-down transformer to cut your voltage in half upstream of the rest of the circuit.

Then came a follow-up:

Thank you for your reply; it was a big help. I am going to be doing the variable transformer one. I have been looking for stuff, but wow its hard to find anything that is needed.

I didn’t like the idea of using light bulbs, so I wanted to get Power resistor 200w 100 ohm but no one sells them, any idea of other Power resistors that I could use?

Try eBay.

I found several by a simple search for 200 watt resistors on eBay. You could vary the search for whatever power and resistance values you want, or use a search to find a good seller, and then ask them if they have what you need.

There are also a wide variety of variable transformers on eBay. But these heavy items cost more to ship, especially internationally.

Before the internet, I always shopped an electronics salvage store in my county. Many cities have at least one of those. Some junk yards and metal salvage yards also have a room full of gizmos that seem too nice to melt down. Call around.

Note: If you are not comfortable rewiring a lamp or replacing an electrical outlet, then you are probably not qualified to build your own anodizer. Buy a read-made regulated 0-150 vdc power supply.


How can I make some of those Fancy Titanium Colors?

March 21, 2008

Another question from a visitor to my regular site:

I’m starting to anodize on my own. How do they create that color “oil slick” in the picture or the “rainbow”?


The many simple colors are all based on voltage, as described in my anodizing page.

The stripes are made by masking off areas with something waterproof, like automotive striping tape. Then anodize to a high voltage color. Then remove the tape, and anodize to a lower color. The high voltage color blocks the lower voltage colors. Voila, stripes!

The rainbow can be made in several ways. The fastest is to turn the voltage up and the contacts off, immerse the piece,  then turn the contacts on and draw the piece out of the electrolyte. The color is now dependent on the immersion time rather than the voltage setting.

The oil slick is trickier. This is probably done by sponge or brush anodizing (clip the positive lead to the piece, and the negative to something absorbent soaked in electrolyte. Then very carefully apply the high voltage wet thing to the charged piece. Rubber gloves and goggles are required. If metal touches metal, then you are practicing welding. Bright sparks, damaged pieces, and possibly damaged electronics.


Can you make red anodized titanium Jewelry?

March 20, 2008

The short answer is: “No.”

In detail, the colors are caused by a particular trick of physics: Optical Interference. As is described in detail on this page, the colors are limited by the behavior of photons. There is no dye or coloring agent to give us precise control.

Red, in particular, cannot be produced because it’s wavelength is twice as long as blue. So if the interference allows red, it also allows the shorter blue through. This creates the secondary color called Magenta, red-violet, or purple.


Uneven results from dimmer switch anodizer

March 18, 2008

Here’s another question I frequently get:

I followed your instructions on building an anodizer and I would like to say that you have made a great job illustrating it. My anodizer is the dimmer and light bulb type it delivers a maximum of 160 Volts.I prepared a solution of TSP in distilled water placed the cathode (aluminum foil) and the Ti at the anode ran the circuit. The voltage keeps rising slowly and I get shades instead of definite colors (mostly violet, golden and pale blue). I can’t hold the voltage at a definite value. What should I do to get smooth colors? I tried adjusting the voltage first then immersing the piece but the voltage after immersing is lower than what I’ve just set it to. Please help me out here and thanks in advance.
David S.

First of all, the dimmer based voltage control is going to be a bit temperamental and unstable. But I used one myself for years before replacing the dimmer with a Variac.

Aluminum should work for a cathode, but should be lightly sanded to remove the invisible insulating oxide layer that spontaneously forms. I usually use titanium, but have been told by many that stainless steel works well.

When you have a large capacitor smoothing a the choppy dimmer voltage, the top end will be a bit mushy. The lower voltages are the worst for this effect. The tan, violet and blues are at the low end of the voltage scale.

Another issue in getting smooth colors is getting the voltage everywhere simultaneously. You should have the piece to be anodized immersed in the solution before completing the circuit to the leads. That is, you need a switch to turn the leads on and off, while the anodizer is running at the voltage you want.

Cleaning and chemically etching the metal before anodizing also helps assure a uniform color, and is generally considered necessary for getting the higher voltage colors.

The voltage measured on the leads or capacitor will drop when you start anodizing, and should rise back to your preset voltage in a minute or so. The time depends on how big a piece you are anodizing, how big your cathode is, and on the efficiency of your electrolyte.

Another possible problem might be the material of your attachment to the anode piece. Only titanium or niobium should touch the electrolyte at the positive side. Never use copper wire or regular (galvanized or tinned) alligator clips to immerse your piece. The current will just go though that, and little will be applied to your piece.