hi. we just opened milling/dental lab using 5-tec. we had couple cases that went out and they are complaining that yellow/green color is coming out near margin area after porcelain were applied. those were milled using ice block. stained dipped with zirkon zahn colour liquid. any solution? coping looked fined. im guessing that it might be the liner... is there solution to do? also, what is good material to use for bonding porcelain to zir? thanks.