If the silicone apppears to be unexpectedly thick when decanting. Some common causes. a) Stored in very low temperatures. b) Stood for a long time. c) Old product getting close to shelf life.
Most of these problems can be rectified by bringing silicone up to room temperature, then mechanically mixed with a mixer drill and paint paddle for a period of time. This will re-blend the oils and fillers into the silicone base giving a consistant blend throughout the silicone and ensuring a consistent 'Shore A' value. As good practise all silicone base, should be thoroughly mixed prior to use to ensure a consistent result, as fillers will settle in time.
Silicone cures softer than expected. Assuming that the silicone base is thoroughly mixed prior to use then the common cause is catalyst ratio. Common ratios of catalysts are 5% or 10% additives. 10% additives are normally 5% catalyst with added oil to give a 10% additive, this is done to give an east calculation when weighing.
Because 10% catalyst is a blend, the separation of oil and catalyst can result. Shaking the catalyst in all cases before use will ensure the catalyst is properly mixed.
Cured silicone has uncured or softer areas of cure. The catalyst has not been thoroughly mixed into the silicone. Many catalysts come as clear or slightly yellow, but when added to silicone it is impossible to see how well the catalyst has been mixed into the silicone and can result in softer or uncured silicone. Catalysts can be pre-coloured allowing a visible measure of how consistently the catalyst is blended into the silicone.