All furnaces require periodic cleaning to minimize the accumulation of various contaminants. Titanium alloys are reactive and have an affinity for contaminants such as oxygen when the part is heated; these contaminants collect on the part surface. Professional furnace companies have documented processes that help control the furnace cleaning process and frequency of cleaning. The first time I visit a furnace company, I make it a point to check documentation that controls their furnace cleaning processes. One of the key steps I look for is frequency and temperature of furnace burn-outs. These burn-outs should be above 2000 F (1093 C) and are usually followed by a wipe down of the inside of the furnace.