Damascus steel is a material made from forged layers of different steels. These different steels etch differentially from one another giving beautiful layered patterns in the steel.
These billets are made up from 3 steels 15n20 EN42J and cs80. The en42J both etch different shades of grey and the giving subtle depth to the pattern, the 15n20 etches bright giving some bling! These are the standard steel I use for my damascus and behave very well together expanding and contracting at similar rates and heat-treating at the same temperatures. The 2% nickel in the 15N20 remains bright when etched and the differing manganese con tents of the CS80 and En42J give a subtle contrast of differing greys in the pattern. This results in the beautiful wood grain and undulating twist patterned that the steel is famous for.
My damascus is forged in a flux free process using my 50 tonne press and Alldays and Onions power hammers and rolling mill. I weld in a reducing atmosphere forge and use no flux in the process.
The as forged damascus is sold with forge scale on it and has not been normalized and heat treated. It is suitable for use for forging out blades. Buying material like this makes it a lot cheaper than if it has been surface ground and heat-treated. You can also grind blades from this material but you will have to grind through the scale (if you want to the scale can be a nice feature and is often left near the spine in Japanese style kitchen knives.) The big advantage of forging a knife to shape is that the valuable material goes a lot further than if you were grinding from stock
Twist pattern steel looks quite different depending on how far you grind into it, the pattern goes from very linear maiden hair into the typical cross and loop patterns seen on Viking and Saxon swords. Have a look at the pictures above for modelled examples of how the pattern changes as you grind through it.
Heat Treating instructions
I apply anty scale compound to my blades when I normalize and harden them. Normalize Damascus steel at 800C and then air cool. I would recommend 3 normalization cycles. Austenise at 800C and hold at temp for 5 minutes. Harden by quenching into a fast quenching oil pre heated to at least 40C. Temper immediately at temperature ranges between 180C and 250C . I temper kitchen knives at 190C or 200C and choppers at 220C and axes at 250C. To soften for drilling I recommend a sub critical aneal, heating the steel to 700C or dull red if you do not have a heat treatment oven and allowing to air cool. If necessary repeat a few times.
Grind all decarburised material from the blade prior to etching. (Hardening will often leave a thin layer of decarburised material on the blade this needs to be removed as it can look patchy in the etch. Grind to 400 grit then clean off all fingerprints with clean 800 grit abrasive on a rubber block. I find abrading the blade gives a better finish than acetone or washing up liquid and hot water. Etch in 1/3 strength ferric chloride until desired depth. Neutralize the blade in bicarbonate of soda solution and then clean in hot water and washing up liquid and rinse with cold water. Ferric reactivity is very dependent on temp. and I find etching can be as quick as 5 min in the height of British summer and take many hours in the winter. A darker contrast can be had by first etching in ferric and then transferring to 50X strength instant coffee. Neutralize as normal after coffee.