▁lies ▁under ne ath ". ▁ ▁As ▁with ▁most ▁Chinese ▁red ▁gla zes , ▁the ▁main ▁colour ing ▁agent ▁is ▁co pper ▁ox ide , ▁fired ▁in ▁a ▁reducing ▁atmosphere ▁( without ▁o xygen ); ▁finishing ▁them ▁in ▁an ▁ox id izing ▁atmosphere ▁may ▁have ▁been ▁part ▁of ▁the ▁process . ▁ ▁From ▁the ▁late ▁ 1 9 th ▁century ▁on wards , ▁usually ▁after ▁length y ▁experiment , ▁many ▁Western ▁pot ters ▁produced ▁versions ▁of ▁the ▁Chinese ▁gla ze , ▁which ▁is ▁techn ically ▁very ▁difficult ▁to ▁achieve ▁and ▁control . ▁ ▁For ▁Chinese ▁cer am ics , ▁some ▁museum s ▁and ▁books ▁prefer ▁the ▁term ▁" s ang ▁de ▁bo e uf ", ▁some ▁" ox blo od ", ▁in ▁both ▁cases ▁with ▁varying ▁use ▁of ▁hy ph ens , ▁and ▁capit als ▁and ▁ital ics ▁for ▁" s ang ▁de ▁bo e uf ". ▁ ▁The ▁most ▁common ▁Chinese ▁name ▁for ▁the ▁gla ze ▁is ▁lá ng y á oh ó ng ▁( 郎 <0xE7> <0xAA> <0x91> 红 , ▁" L ang ▁kil n ▁red "). ▁Another ▁Chinese ▁name ▁for ▁this ▁type ▁of ▁gla ze ▁is ▁ni ú xi ě h ó ng ▁( <0xE7> <0x89> <0x9B> <0xE8> <0xA1> <0x80> 红 , ▁" ox - blo od ▁red / s ang ▁de ▁bo e uf "). ▁ ▁Chinese ▁sang ▁de ▁bo e uf ▁ ▁Origin ▁as ▁im itation ▁of ▁M ing ▁war es ▁ ▁Sang ▁de ▁bo e uf ▁gla ze ▁was ▁apparently ▁developed ▁around ▁ 1 7 0 5