Why dose my oil base paint always have a scum on top of it the next time i use it?usely a few day latter!?

hiya coondog...





the ';scum'; you refer to is most likely one of two issues that are common with virtually all oil based products...





1) if your paint has developed a layer of skin, that is the natural progression of oil based products...oil based paints cure (dry) by oxidation - the skinning is the result of wet paint coming in contact with oxygen molecules in the can to form a film...





2) if your paint just has a clear murky liquid on the surface a couple of days after you've used it - that is not your oils separating as was mentioned earlier...that is actually a solvent float (usually a combination of slow drying thinners and alcohols), designed by the manufacturer, to keep the oils and alkyd resins from coming in contact with the oxygen molecules within the can so the paint will not begin to oxidize. this ';float'; of slow evaporating solvents is called a synoreces and is becoming more common in the manufacture of oil based products...





if this seems to be a recent phenomena that you're experiencing, it is due to the governments ever changing v.o.c. (volatile organic compounds) regulations governing all manufacturers in the types and amounts of solvents they may use in the manufacture of oil based products.





in either case (skinning or solvent-float) the solution is fairly easy...in the case of skinning, simply, and carefully remove the skins with a paint paddle and throw away. be careful not to stir skins back into wet paint 'cause they'll never re-wet and become paint again - if you do, you'll be picking out small chunks or goobers from your finish product. to keep this from happening again, you can create your own synoreces by pouring enough paint thinner (mineral spirits) on top of the remaining paint to be stored - allow the thinner to set on the surface - do not mix in with product until you're ready to start painting again...





in the case of solvent float (synoreces), just stir it back into the paint thoroughly and begin painting.





someone mentioned earlier to add penetrol to oil base products. penetrol is made by the flood company and is a proprietary blend of oils and solvents - while there may be some advantages to using a product like penetrol - it will help to reduce drag and provides for better flow and leveling. it will lower the surface tolerance resulting in better penetration into porous or profiled surfaces but also slightly lowers the film build resulting in diminished protection to the surface. penetrol is a unique product and does provide some advantages in application, however most paint manufacturers warn that any warranty will be negated by the addition of such product. regardless, penetrol will not help or change the situation you have described.





i hope this info is helpful to you...it's refreshing, but becoming rare to find someone still willing to use oil based products anymore...good luck on your projects.Why dose my oil base paint always have a scum on top of it the next time i use it?usely a few day latter!?
That is what paint does. Stir it before you use it.Why dose my oil base paint always have a scum on top of it the next time i use it?usely a few day latter!?
store it upside down then the scum/skin will form on the bottom instead of the top.
The can may not be completely sealed, sounds like air is getting to the top of the paint and the top is starting to dry.
That would be the oil seperating from the paint..just like the way the oil in salad dressing always seperates and rises to the top
I am a painter, I use an agent for my oil paint, It makes it last alot longer and the finish quality of the paint job will be incredible. It is called PENETROL, you mix it in with the oil paint so it sort of levels out when you use it, als makes the paint last longer, nice stuff, you can get it at Home Depot (white and orange tin can) in paint dept