Hey guys, I switched over to using preshaded katana zirconia about a year ago and have started to notice alot of our shades look low in value and sometimes too yellow. I am sure this is from a contamination in my sintering furnace (which is a duotron). To replace the heating elements B&D wants $500 a piece which there are four of them. However I can't justify that at the moment and the heating elements don't look bad to me and there is no build up or discoloration that I can see. Do any of you guys know what other options or a troubleshooting process I can go through to fix this issue without dropping 2000 on heating elements. I ordered a product from Vision USA called Purge sinter but I am not sure if this is the issue or will fix it. This does not happen on every unit or every firing cycle only some units on some firing Cycles which leads me to believe it also may be an issue with my trays or centering beads do I need to purge them as well if so does anyone have a program they recommend or process they recommend. If not does anybody know of a 3rd party manufacturer of heating elements that are not outrageously expensive. I've looked around and can't seem to find anyone with a used sintering furnace for sale but at this point I've got to figure something out cuzit's killing our production. Any insight or advice will help.