There are two problems that new users sometimes have with Castaldo® QuickSil 2 - part RTV putty silicone molding rubber.
The rubber may not become firm after the 15-minute cure time. Or the rubber becomes firm but the outside surface remains sticky and soft.
Both complaints are the result of OVER-MIXING. The solution is to MIX LESS THOROUGHLY.
Careful workers often think that they should mix part A and Part B until a uniform color is acheived. This is logical thinking and a good practice in general, but in the case of QuickSil it can lead to hardening problems.
People who have made bread and kneaded bread dough know that some kneading is important but that too much can kill the bread - that it will never rise or bake properly. The same is true with QuickSil.
A better approach is to mix the two parts quickly - about 1 or 1.5 minutes is usually enough - and then leave the rubber alone. A streaked or mottled appearance is OK. There is no need to mixit thoroughly!
This is almost right - just a little more mixing is required.
Uniform color like this is NOT NECESSARY and may cause cure/hardening problems.
Another problem is that the suface of an impression in QuickSil is ruined by the appearance of bubbles or blisters in the rubber. These do not appear throughout the rubber, but only against the model.
This problem does not often appear in molds made using a press but instead is occasionally reported in impressions made by hand pressing.
When insufficient pressure is applied, oil in the rubber can form a pocket or bubble. More pressure will keep the oil in the rubber and not allow it to escape. The solution is to use more pressure. Even ordinary
C-clamps will do.
For more in formation, please see the QuickSil instruction sheet that was supplied with the product or go to Using QuickSil page.