How can I get consistent colors?

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.

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5 Responses to How can I get consistent colors?

  1. Bill Seeley says:

    Ahhh yes, the desire to digitize the process. We decided early on in my research that there were just too many variables.

    In the end, it is the eye of the processor that judges the final color. The history of the metal itself can have much to do with the outcome. This we seldom have knowledge or control of. Every step that you can must be controlled, repeatable, uncontaminated…

    If pieces are bigger the contacts should also be bigger or more of them. The leads to the contacts may also have to be of a heavier gauge.

    Do you have full voltage and current control? Is it a solid state anodizer? If the product reaches the voltage but the color is way off then I begin to think there is a surface contamination problem. The same is true if it never reaches the set voltage.

    Like I said so many, many variables.
    If you are serious about this, then nail down every variable that you can.
    First test color the material as received. Does it work?
    What step is next? Does it work after that? Continue step by step…
    Eventually the answer will be clear.

    Bill

  2. Peter says:

    Wow that was quick. Thank you for that. The answer is helpful in so far that I understand that I have to record from now on what I do. Because I always use the same titanium in the same thickness I should be able to draw a line after some time. I am going to take the weight of the pieces. And since I take the same thickness with exactly the same finish every time. I should be able to establish a relation: weight (= surface) + voltage = x colour.

    This is going to be fun (read: I hate this) I rather design and make the pieces.

    If I establish a usable link between weight, thickness, grade, and voltage versus colour I get back to you.

    It is great that there are people out there that are willing to share there knowledge. Thank you for that.

  3. Maggie says:

    Now I understand why the batches of colors of anodized Niobium and Titanium are always different from one and other when I order them. I think I’ll continue to leave the anodizing up to those of you who are experienced with it.

    Although if anyone manages to get even close to a passable “gold” tone on a consistant or semi-consistant basis, I may just jump in and give it a whirl ~ or make an investment to purchase it. I know of a large market for it! 🙂 Dan did achieved the tone, so it can be done. I only wish I had ordered a hundred pair instead of just 2!

    For those of us who prefer the more traditional colors of jewelry metal (silver and gold) the natural colors of Titanium and Niobium are “do-able” for the silver lover, but anodized yellow usually doesn’t even come close for us gold lovers.

    New Question:
    What can be said about the Sparkie Welder? And how available is Niobium Fusion Findings?

  4. James W. says:

    Another variable may be temperature. I find that cooling the TSP and container down in the refrigerator and using a ice water bath seems to help.

  5. MrTitanium says:

    Cold is better? I’d heard that hot is better, both because the gas saturation in the fluid is much lower hot, and chemical reactions go faster in hot.

    Now, I have to try it both ways from “normal” to see whether I can detect a consistent difference.

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