I'm looking for information on how mill scale forms during the
steel-making process (i.e., the atmospheric conditions, mechanical
processes, heating and cooling profiles), with the ultimate goal of
being able to recreate mill scale in a small shop/studio environment.
The reason for this is that I would like to incorporate the look of
mill scale in some of my sculptural work, but the processes involved
in creating the work tend to destroy or degrade the original scale. No
other coatings or processes I've encountered yield quite the same
color, texture, uniformity, and overall look of mill scale. Any
thoughts or suggestions?
Boy, I get lots of scale when I put steel into a propane forge! Do you
know any blacksmiths? Heat the steel to cherry red in air - that oughtta
do it. Actually, that scale isn't quite as tight as mill scale.
What I have done also is to do blending with a sandblaster, using a very
light sand sweep. However, your cosmetic requirements are likely to be
tighter than mine were.
I share studio space with a blacksmith, and do some smithing myself,
but the scale from the propane forge isn't nearly as uniform nor quite
as adherent as mill scale, and it doesn't have the same color. I
suspect the former may be due to the turbulence, hot spots, etc., that
occur in a small forge, and the latter may be due to oxygen
concentrations and heating profiles, but that's just a guess at this
I have heard that propane forges don't produce the same type of
scale as a coal forge (something along the lines of less contaiminents
in propane). So if the blacksmith is willing to try purchase a coal
forge you might be able to get the type of scale you are looking for
(though he might know someone with a coal forge that you could just borrow).
Ken Vale wrote: I have heard that propane forges don't produce the same type
of scale as a coal forge (something along the lines of less contaiminents
in propane (clip)
How about throwing some lumps of coal in the propane forge, to introduce the
A rose by any other name. Mill scale is black iron oxide, ie.
FeO. It occurs when iron or steel is heated above approx. 1000?F. in
the presence of excess oxygen. Above 1500?F scaling can be very rapid.
I know what you are trying to accomplish Bert. Anyone who fabricates
with steel and wants to maintain natural mill scale surfaces has a
problem. I have a friend who used to make steel furniture and even
though he used welders and grinders he was able to obtain an evenly
scaled final surface. You might not like this solution but it does
work. You need to have a box furnace big enough to hold the work. As
the final process, the entire object is heated slowly & evenly to a temp
of about 1200?in a slightly oxidizing atmosphere then held there for
several hours followed by a slow cool down. An exact heating cycle would
have to be by trial and error. Temp, time, and atmosphere are the key
variables. I have tried "touching up" disturbed areas with a rosebud
heating tip with mixed results (mostly unsatisfactory) If your work is
large you better find a friend that works at a steel mill or a heat
Good luck dude,