Wednesday, April 1, 2009

Colouring the experiment

Every once in a while, somebody asks me to colour metal. Steel is funny stuff, it actually colours fairly easily, providing you stick to some fairly straightforward colours. The breastplate in the picture below was baked in order to colour it. I was curious as to how it would look, so I picked out a really ugly old which had rust spots on it, and a weld line up the centre. The results were interesting. A lovely plum colour came out. If I had allowed it to continue baking for another 20 minutes, I suspect it would be almost perfectly "evening sky blue".

The colour is easily visible on the picture above. No paint or anything has been added in any way, just a judicious application of heat.

The heat treatment didn't help the discoloured metal seam up the front. I was wondering if it would disguise it. No such luck. Oh well, it just means I will have to do a good job of sanding off any existing stuff before baking the metal. In the above pic, you can see the slight surface rust, on the right breast. The colour was the same, but the texture sort of gives it away...its not as shiny as the rest of the steel.

This above picture is just from a different angle...the colour really came up nicely. I will give it a coat of lacquer which should keep the colour nice for years. I think the light is reflecting a little more off the top centre ridge which makes it look a little brighter. This could be used to create an effect.

The traditional way this colouring method is used is to create a relief pattern in the metal with punches...and then heat treat it just as I did here. Then sand off the high spots, leaving shiny surface with a dark background.

Any paint left on it will discolour differently than the background, including any oil, wax, and especially finger prints. The usual flaw in these jobs is that there is often a very slight residue on the metal surface caused by a tiny bit of oil left on the rag when you clean it. Results in swirly patterns on the surface instead of a nice even colouring. Nothing to do when that happens except bring it back in and sand it again. I prefer electric sanders for this purpose since air powered equipment spits out a fog of oil which puts paid to any possibillity of keeping it clean. All varnishes and laquers must be cleaned off as well. You can't even use the old armour's standby cleaning fluid (lacquer thinner) because it frequently has some oil dissolved in it which deposits when the thinner flashes off.

To make this job even more nasty, you have to clean with super flammable fluids, then heat treat them in a very hot oven. The potential for a flare up moves from "possible" to "likely" when you have hot ovens in the same room. I like to do this job on rainy days just to limit the possibility for static electricity. And I still use long sleeved cotton shirts, long cuffed gloves and face shields when I do it. As long as you are ready for it, the panic factor goes way down.

I wonder if the clients will accept hazard pay billing?

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Anonymous said...

You could try a degreaser, such as the ones used to prep metal before paint for body work, etc. Though they are hilariously flammable. You would probably want to rinse in distilled water afterward to start with, but it would definitely be an outdoors faraway from the heat source thing.

kimberly said...

Lovely color!

Doesn't all of your work deserve hazard pay??!!