ammonia fuming
... that the technique of darkening oak by ammonia fuming was discovered accidentally when boards stored in a stable were darkened by fumes from horse urine?
... that the technique of darkening oak by <b id="mwDAM"><a href="./Ammonia_fuming" id="mwDAQ" rel="mw:WikiLink" title="Ammonia fuming">ammonia fuming</a></b> was discovered accidentally when boards stored in a stable were darkened by fumes from horse urine?