What is cissing? Does this appear in polyurethane paints specifically? How can this condition be corrected? Is there some additive that can be used to solve this problem? V.J.
Although I have heard it used in the past, "cissing" is not a common term used in the United States today. Therefore, to answer your questions, I searched my archives for references. The National Paint Dictionary, 2nd ed., by Jeffrey R. Stewart defines "cissing" as follows: "The British term for crawling." It defines "crawling" as follows: "The tendency of a liquid to draw up into drops or globules as a result of an abnormally high degree of surface tension." Stewart's Scientific Dictionary, 4th ed., (previously called the National Paint Dictionary) gives the same definition for crawling. It goes on to say the following: "Oil paint applied at room temperature over a cold or greasy surface may also cause crawling. Other causes are the application of a glossy coat of paint over a fresh glossy coat...the application of paint or varnish over previous coats that are not hard and dry...the presence of moist finger marks on the surface...the presence of a thin film of wax."
The 1951 edition of Paint Film Defects by Manfred Hess defines cissing as follows: "Partial creeping back and contracting of the film with formation of indented or beading border-lines and/or uncovered islands or even only pinholes, where the bare substratum becomes visible." He goes on to say, "Cissing is in a broad sense due to bad wetting...Greasy or damp surfaces promote bad wetting...As foreign contaminating matter may be responsible for the defect...the time interval between cleaning and painting should be kept at a minimum..." This dissertation goes on for four pages and space does not permit me to print it all. However, Hess does suggest using pine oil or turpentine to promote wetting and retard drying. Don't try this at home kids. Furthermore, don't add pine oil or turpentine to your polyurethane.
Finally, the 1995 edition of the Paint and Coatings Encyclopedic Dictionary published by the Federation of Societies for Coatings Technology defined cissing as follows: "A slight shrinkage of a glossy paint coat resulting in small cracks through which the undercoat may be seen; a mild form of crawling."
The aforementioned is probably more than you wanted to know about cissing. Owing to space constraints, I will be brief in the answers to your other questions. Cissing can occur in paint films using resins other than polyurethanes. The condition can be corrected by cleaning the substrate to remove oily soils, moisture and other contaminants. Additives may correct the problem. However, I recommend asking your paint supplier about additives that can be used specifically in his paint.