[TheForge] preserving heat colors

[Clyde]

Hochewa is right. I had an article on this but can't find it. It dealt with
copper but the refraction thing is the same. Here is an old I found that
gives some hints on possible coatings to preserve the color as best you can.




Bill Woolley said,
>Refer to a good welding manual or general metalworking text for
>specific information on the colors produced at various temperatures.
>Remember that this produces an oxide on the surface that can be removed
>with a wire brush etc. if you are unhappy with the final results of your
>treatment.  As far as permanence goes, I would be glad to hear from
>anyone with concrete, time tested methods of fixing this oxide
>cheers,
>Bill Woolley
>

Hello Bill & everyone else,
Any oxide on the surface of steel can be "fixed" by simply sealing the
surface against atmospheric moisture. If the surface is allowed to contact
any moisture, the oxide color will change and eventually look just like
plain old rust because the oxide crystals on the surface of the steel that
produce the color will change and grow. Oil or silicone sprays can be used
for this sealing, but are not very permanent. You mentioned the product
"Extend". This is a Cyanoacrylate based material that is painted on to the
surface of steel to provide a barrier coating to moisture. It is sold as a
rust proofing for steel. There are several companies that produce
Cyanoacrylate based coating materials similar to Extend.

Super-Glue is a Cyanoacrylate based material that most of us are familiar
with. These Cyanoacrylate based materials react with moisture and
polymerize to a hard coating. The moisture that is present in the oxide on
the surface of the steel is absorbed by the Cyanoacrylate material during
the curing reaction so that no continued "rusting" occurs after the
coating is applied because there is no longer any moisture trapped within
the oxide crystals on the surface of the steel. Acetone can be used as a
solvent for these Cyanoacrylate materials to produce a thinned "wash" if
desired. The thicker the coating the more it will look like it has been
painted due to the reflectance off of the coating.

Epoxy can also be thinned with acetone and applied as a thin coating (very
thin if you desire) to seal the surface and block moisture from getting to
the surface of the oxide on the steel. Polyurethane can also be used in
the same way. If you thin epoxy or polyurethane with acetone or MEK, make
sure to properly mix the resin and hardener together first and have it
well mixed before adding the solvent to thin it. The epoxy or polyurethane
could also be applied over the top of a Cyanoacrylate coating to add
greater durability, but any top coat applied over the Cyanoacrylate coat
must be applied within a very short time span after the Cyanoacrylate is
painted or else the Cyanoacrylate coating when it is fully cured becomes
very difficult for any top coat to stick to it. This is also true of
double coating with Cyanoacrylate. The best policy is to top coat as soon
as the Cyanoacrylate coat becomes non-tacky.

I have used these materials in their clear forms to top coat copper oxide
and gold artwork. The black or brown copper oxide is very easily damaged
or changed by moisture and needs a protective coating. I have used epoxy
and super-glues thinned with acetone (10-30% epoxy to 70-90% acetone) to
use as a spray coating over the oxide. I didn't want a very thick coating
since the oxide is a very matte, non-reflective surface, and any
appreciable thickness of a coating causes its appearance to change and
become light reflective and doesn't give quit as good of an appearance
contrasting to the highly reflective gold plated surrounding surfaces.
With these thinned coatings, I could apply one coat at a time until I
achieved the desired thickness and appearance. If thinned sufficiently,
the epoxy coating will not fill-in the surface of the copper oxide, but
will just barely coat each oxide micro crystal with a coating that is only
several molecules thick. It doesn't take a very thick coating to produce a
vapor barrier to atmospheric moisture for indoors situations. For outdoors
applications, you will need a regular heavy painted coating.

The best of luck in your work,
Brent Wiscombe
bwiscombe at msn.com
Mesa, AZ




To All,
Heat colors are not the color of the oxide that has formed.  The oxide
actually is transparent and the colors you see are the refraction of light
just like
a prism.  The oxides in thickness are multiples of the wavelength of the
color you see.  When you add a protective layer you add to the thickness of
the
refracting layer and you change the color.
I ahve done several pieces that also have gone much more blue than I wanted
but they also retain other colors.  It appears that if you thin the oxide
layer
you put on at first and then add a layer of acryllic you may end you where
you want to be.  If the pieces are for indoor use maybe a thin layer of
really
good wax may be enough.
I like the effect ot the temper colors.
Keep playing with them.  You may find something we all can use.

Regards,

Hochewa