Understanding 'Shiners' and Plasticizer Migration

What happens here

The discussion addresses the phenomenon of 'shiners,' which are shiny spots that appear on painted caulk, particularly noticeable with darker colors or flatter paints. Rob explains that shiners are caused by 'plasticizers' (a type of oil or solvent added to improve flexibility and reduce brittleness) migrating through the paint film. This migration changes the paint's gloss and can leave a tacky surface, which is not only a visual problem but also affects the caulk's long-term performance by reducing its flexibility and potentially leading to cracking or 'banding' along the joint. He notes that Tower Sealants specifically formulates products to avoid this issue by balancing components and, in some cases, not using plasticizers.

Goal: Learn about plasticizer migration, its causes, and its impact on painted caulk.