My company used to do a hot black oxide for stainless steel in
house. Its not beyond the reach of a small studio but its not a nice
The process - I’ll use the brand name of the chemicals I used - all
from Electrochemical Products Incorp. (EPI). MSDS’s would tell you
the active ingredients - I can tell you they are all either very
basic or very acid. I literally worn a rubber glove and a high
quality gas mask for a 12 hour day in a 100+ degree room - this is
the reason we not outsource the process.
Clean in a hot industrial detergent - Eclean at 200F
wash very well - the chemicals from each step do no play well
with each other - no explosions just detracts from the effectiveness
of the chemical
etch the surface of the stainless - Epik at about boiling - if
you are doing mild steel you can use a simple etch like Hydrochloric
wash very well
Immerse in boiling blacking solution (Eblack) for about 15
minutes - temperature must be monitored carefully. The boiling point
changes with the concentration and the need to keep the contention at
the right level for it to work.
Wash very well
Seal with a light water based oil for stainless - for mild steel
I used WD40
Equipment list for my 20lb batch sizes set up for each step - all in
a dedicated 300 sq ft room with the biggest exhaust fan I could find.
Also equipped with water, nat gas, and waste water storage system
(all waste water was picked up)
digital thermometer, 5 gal enamelled steel pot, electric hot
laundry sink #1
3 gallon beaker on a propane camp stove - need glass as the Epik
will eat through a stainless pot in about an hour. Beakers were a
problem as they were breakable and boiling Epik was dangerous and
highly acidic - I had a pail of baking soda at the ready.
laundry sink #2
30 gallon custom built steel tank with insulated sides and a
50,000BTU natural gas bbg burner hooked up underneath. It is
critical that the solution does not drop in temp when you dump in the
load. The tank needs to be oversized and with a good sized burner.
Its also a tank of saturated salt at the boiling point and it needs
to be very uniform temperature - it took me 3 hours to get the tank
going - this meant if I fired up the tank I was planning a full 12
hours of blackening.
What I learned - mild steel is way easier then stainless
If you can handle 300 lb batch sizes pay the pros - we pay $90 for a
300 lb batch. I could do about 40 lbs per hour ($12 per hour). For me
the only benefit to doing it myself was I could do small batches.
When I did it I offered maybe 40 products blackened - now I pay for
300 lb min batches and offer about 12 blacked products.
Let me know if you have any questions.
The Ring Lord Chainmail