I'm missing something with the bread and saw blade trick. Unless
you really carbonize the bread there is still water present... the
temperature CANNOT go above 212 F (100 C) Way too low for any
tempering. Might as well stick the blades in your coffee and save
the bread.
We are not trying to temper it. We are trying to age it. When metal
is taken to high temperature atoms of iron and carbon moves at
different rates. When metal is cooled rapidly, carbon is arrested by
surrounding iron and carbon is not in its proper position as related
to crystal structure. Tempering is a process of re-crystallization
to allow carbon find it’s place. However, to do it perfectly, we
would
have to heat each and every atom of carbon at different temperatures
depending on exact location of atom. The reasons are that one atom
maybe almost in the right spot and needs little amount of energy to
get to it’s place, while another atom may be far away and needs more
energy to get into position. We obviously cannot do that. Heat is
applied evenly and that causes some atoms to overshoot, some
undershoot, and a few will wind up where they suppose to be. That
result in the alloy which is fine in general, but far from perfect.
The process of re-crystallization will go on forever, unless we
store metal at absolute zero. From experience we know that couple of
year at room temperature will do the trick as far as goldsmith is
concern. The process of baking inside the bread is simply to
accelerate this process. Bread is a temperature control device. If
one have an electric oven and quartz sand, overnight in the oven
buried in the quartz sand works even better. Temperature should be
under 212 Fahrenheit. At 212 degrees atoms start moving to fast. 160
to 180 degrees probably the best range. Process can be repeated if
desired or modified. 2 nights at 140 may work just as well or better,
and so on…
We want to give every atom just enough push so when it gets close to
the right location, it would be arrested by internal forces which are
responsible for maintaining crystal structure. Think of it like black
hole in space. Once object gets close enough so attraction overcomes
inertia, atom gets sucked into the position and remains there until
the metal gets heated again. We want to maintain this environment
where atoms have enough energy to wonder around until enough of them
would find proper places to form crystal structure of required
properties.
If it helps, think about aging wine, cheese, and etc. The process is
the same. Can a wine be drunk right after it is bottled ? Sure it
can, but it is so much better after a few years. So are 8/0 blades.
Leonid Surpin
www.studioarete.com