In order to see the pattern in your Damascus, whether it be Carbon or Stainless, Damascus or San Mai, or just a differential quench on high carbon steel (Hamon), you will need to etch the metal to reveal the pattern. Pattern welded Damascus and laminates (San Mai, Cu Mai etc) use metal combinations that etch differently to create contrasting colours. Differential quenching (Hamons) creates different structures in high-carbon steel that, again, etch slightly differently to reveal contrasting colours.
Etching needs to be done after Heat Treatment and when all shaping and surface prep has been completed.
SURFACE PREPARATION
Surface preparation is the key to good etching. I feel a 600 grit finish is the absolute minimum level and I normally take that finish up to 1000-1200 grit. I then go to the sink and scrub the surface, using washing-up liquid, with my final grade abrasive or a fine Scotchbrite scourer. Rinse under running water until the water fully wets the entire surface. If the water “balls up” on any part of the surface repeat until you are certain the entire surface is clean and free of all oily residues. If you’re not sure – scrub again. Once clean DO NOT TOUCH THE SURFACE AGAIN AND DO NOT LET IT DRY. Place your metal immediately into the etchant.
ETCHING CARBON STEEL
For etching carbon steels I use Ferric Chloride. This can easily be purchased (in the UK) as a 40% solution.
Take care when handling Ferric Chloride – the solution is somewhat acidic and you must use suitable PPE. If you’re not sure what PPE to use I suggest safety glasses, acid-proof gloves and immediate access to water for flushing any spillages or skin contact as an absolute minimum. I do not profess to be fully knowledgeable as to the correct handling procedures for Ferric Chloride. If you’re not sure you will need to research for yourself and ensure you are using a safe practice. I do not take responsibility for your safety through this page.
I dilute the 40% solution – 1 part Ferric Chloride to 2 parts water. De-ionised (or distilled) water is preferred and essential if you have a hard water supply. You will also need some bi-carbonate of soda to make a neutralising solution. 3-4% bicarb on any tap water will be OK.
Your carbon steel component must be hardened and tempered. You will not get good contrast on annealed or normalised steel. The etchant also needs to be warm enough to react in a reasonable time. I suggest 20 Celcius as a minimum. If you keep everything indoors or in a warm workshop, room temp should be OK. Otherwise, stand your etchant container in a larger container filled with warm water. You won’t need to warm the bicarb.
Your etchant container must be deep enough to fully immerse as much of the blade as you need to etch. topping and tailing in a smaller container will not work and will leave a join line. Your bicarb container can be smaller and topping and tailing is OK for neturalising providing all of the blade is immersed at some point in the bicarb.
Place your cleaned component in the etchant for 5 mins. Remove, rinse under clean water and lightly scrub with your Scotchbrite or final grade of wet & dry abrasive paper. If the contrast looks good, neutralise, re-wash & dry. If you’d like more contrast repeat etch in 5-minute spells until you have what you’d like then neutralise and dry. A final rub over with a very fine paper, I use #2000 grit, can enhance contrast further.
This is not the only way to etch Carbon Steel, there are many good YouTube videos with variations on theis theme. This method works for me though.
ETCHING STAINLESS STEEL
For etching Stainless Steel Damascus you can’t do better than follow the Damasteel guidelines on their website here.