If you reheated it repeatedly and perhaps pickled it in between you
may have inadvertently created reticulation silver from your
argentium: the fine silver has come to the top of the sheet and
bubbled up as you describe from the copper oxides in the alloy being
either burned off or dissolved when combined with atmospheric O2.
You can read about reticulation and reticulation silver on Hoover and
Strong’s website and in many books on jewelry making, and on the
Reticulation silver per se is 80% fine silver and 20% copper.
Sterling and argentium are slightly different alloys argentium
having extra germanium whereas sterling does not typically have that
element/mineral added to it as an anti-oxidant, but all have fine
silver and copper in somewhat similar ratios.
Nonetheless in repeated heating and cooling one’s sheet of silver
alloy and acid scrubbing the surface ( during the pickling process)
the layer of fine silver is concentrated on the sheet and in the
liquidus stage of heating it during brazing/soldering becomes easily
manipulated into patterns that are somewhat predictable but are not
easily recreated over and over exactly in any two operations - the
basic movement of the torch will dictate the approximate direction
the metal will take but getting the same pattern and depth of the
waves and valley and peaks and plains, so-to-speak, requires great
practice and focus if working towards attempting to recreate the
conditions, temperatures, etc. involved in the process. Cynthia
Eid’s expertise should be referenced in your situation. Her
knowledge of the metal alloy is the most sought after and she is the
premiere craftsman/metalsmith working in in Argentium today. Her site
is easily found on the web.
Another possibility is if you fabricated the sheet yourself there
may have been some contaminants in the scrap or crucible or in the
rolling process during or after you poured it. If purchased perhaps
calling the seller or manufacturer and asking for a replacement if it
has happened on more than one piece would be appropriate.
Manufacturers are not 100% consistent all of the time and there is
some margin for error with any maker or fabrication process. Most
will be glad to refund your money or replace the sheet as you desire.
Be a good consumer and call the vendor/manufacturer and explain the
situation and offer your suggestion for a remedy that most suits your