The Impression Stays Sticky or Does Not Polymerize
An impression that stays sticky did not polymerize completely. Something blocked the reaction, or the mix was wrong. Since you cannot measure it, find the cause and take a new one.
Grease, Oil or Cutting Fluid
Grease, oil, or cutting fluid is the most common cause. Machining oils are often invisible, yet they still block polymerization.
Degrease the part before every impression with DN1 or a validated degreaser. Spray the surface, then wipe it with a clean microfiber until it is dry. Never use acetone, because it prevents the product from polymerizing.
A Material That Blocks the Reaction
Contact with latex, sulfur compounds, graphite, and certain titanium alloys can alter polymerization. This list is not exhaustive. Because latex gloves are the usual trap, handle the product and the part without them.
If you suspect the material of the part, extrude a test drop on it before the real impression.
An Uneven Mix
If the test drop shows two colors, the mix is not homogeneous. Keep extruding until the color is uniform before you inject.
With a Manual Putty, take equal volumes and never swap the spoons between the two components.
Cold, or a Product Past Its Date
In a cold workshop, polymerization slows down markedly. Wait longer and check with a fingernail on the test drop.
Check the expiration date. A product that changed in appearance or consistency, or that takes abnormally long to polymerize, may have deteriorated.
