▁can ▁facil itate ▁the ▁rendering ▁of ▁details ▁that ▁would ▁be ▁more ▁difficult ▁with ▁op aque ▁pain ts — e . g . ▁the ▁complex ities ▁of ▁skin ▁t ones . ▁ ▁When ▁multiple ▁layers ▁of ▁gla zes ▁are ▁used , ▁the ▁colors ▁in ▁all ▁visible ▁layers ▁can ▁appear ▁combined . ▁However , ▁the ▁p ig ments ▁are ▁not ▁phys ically ▁mixed , ▁since ▁the ▁paint ▁is ▁left ▁to ▁dry ▁before ▁each ▁success ive ▁gla ze ▁is ▁applied . ▁The ▁artist ▁may ▁apply ▁several ▁layers ▁of ▁paint ▁with ▁increasing ▁amounts ▁of ▁oil ▁added ▁to ▁each ▁success ive ▁layer . ▁This ▁process ▁of ▁applying ▁the ▁fat ▁layers ▁( more ▁oil ▁in ▁the ▁painter ’ s ▁medium ) ▁over ▁the ▁lean ▁layers ▁( less ▁oil ) ▁can ▁minim ize ▁crack ing ; ▁this ▁is ▁the ▁" f at ▁over ▁lean " ▁principle . ▁ ▁Many ▁pain ters ▁ju xt ap ose ▁gla zes ▁and ▁op aque , ▁thick ▁or ▁text ured ▁types ▁of ▁paint ▁application ▁( that ▁appear ▁to ▁push ▁forward ) ▁as ▁a ▁means ▁to ▁increase ▁surface ▁variety , ▁which ▁some ▁pain ters ▁feel ▁increases ▁a ▁painting ' s ▁drama , ▁bright ness , ▁and ▁depth . ▁ ▁Wall ▁gla zing ▁When ▁the ▁technique ▁is ▁used ▁for ▁wall ▁gla zing , ▁the ▁entire ▁surface ▁is ▁covered , ▁often ▁showing ▁traces ▁of ▁texture ▁( F rench ▁br ush , ▁par ch ment , ▁st ria e , ▁rag ▁rolling ). ▁Either ▁oil - based ▁or ▁water - based ▁materials ▁are ▁used ▁for ▁gla zing ▁walls ,