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Troubleshooting Mokume Gane, post-patterning. Flaking Top Layers

Hello All,

Problem: face layer of copper on mokume gane sheet ends up flaking, tenting, tearing off in places.

I am very new to this; my third billet, I made a billet of 8 layers of copper, and 7 layers of fine silver. The layers started approx. 20 gauge, with the top and bottom copper layer, a bit thicker, 18ish.

I reduced with hot at first, then around a quarter inch, i began rolling. I stopped at about 10 gauge and began patterning. I used drills and ball burrs, while annealing and hammering down, then where near flat, rolled out to about 16 gauge.

Things were generally going great, except at the very end. I’m having issues with the final layers of rolling out, annealing, bending/forming.

I notice that top layers, towards during reduction, appear to thin out faster than the middle layers.
I imagine this is due to a few possible factors:

  • (unsure) i understand that using a not-heavy enough hammer during hot work, can cause the layers to thin unevenly? is this true/applicable?
  • oxidization during annealing. I use boric acid/borax/methanol and batterns, but i tend to still get a lot of oxidization with the copper, meaning cleaning, which costs copper via pickling/abrasion
  • not annealing enough during the final rolling? (from 18-22, usually with 1 or 2 annealings during)

Any tips on the end phase of working with mokume?
For cleaning the face after annealing heats, i have been using Sparex. I have acetic acid 10%/salt, sulfuric acid, hydrogen peroxid, and muriatic acid handy. Is there a better/gentler use? Or should i use strong-as-possible pickle and work quickly? Should i avoid pickling all together?

I’ve never had much luck with firecoating/fluxing copper. My silver appears fine, but i don’t know if copper can be protected to the same extent. Any tips for protecting those surfaces while annealing? I coat everything in boric acid/borax, or Batterns, never seems to be even, or perfectly protected.

I have a 3 pound hammer coming in, for a heavier hammer. Can i use a crosspein during reduction, or is that stress too focused?
I also have a 20 tonne press in progress, i’m hoping that will help with even crushing as well. Is there benefit to heating the plattens before crushing?

Thank you so much,