We are in the process of reworking sash from a library at UVA. Our company has been reworking sash for many years. The sash were built in the early 30’s out of pine and finished with lead paint. Our process is to steam the paint off, then when lead paint has been removed we do whatever restoration needs to be done. We use Sherwin Williams exterior oil primer.
Over the years we have reworked many thousands of windows. This batch is causing problems as the oil primer is not completely drying even after four days. On another project we have in the spray booth the same oil primer dries fine. That project is made from sapele. Moisture content and ph on the sash are good, leading us to wonder what is interfering with drying. We need to use oil paint as it is in the specs and also because the glazing we use has adhesion problems on latex.
Any thoughts would be welcomed; we have a job coming up soon with 700 sash so we need to figure this out.
Thanks

Could there be any residual moisture left after steaming? Any way to check w/moisture meter?

Moisture content and ph on the sash are good,

Temperature in your shop?

What does Sherwin Williams say?

I read a long while back about SW low VOC oils taking a very long time to dry and requiring thinner coats. Not sure if it applies to the primers as well. From memory the solution was heat and airflow. Would seem you'd done far and away enough to have the temp and application right. Any input from sherwin industrial?

Tim:

Are you sure that the wood is pine? Was it kiln dried to begin with? (I know, how would you know that?) Perhaps your steam process has brought resins to the surface that may have lain dormant for years, and if it was air dried lumber, the resins would not have been "set", as they may have been if kiln dried. Cedar might be even more of an issue than pine in that regard.

I've heard old wive's tales of finishers "baking" windows and doors to try to set the resin, but that sounds dubious at best to me.

As a practical matter, perhaps an exterior stain blocking primer like Zinsser might be more effective at sealing in whatever it is that is interfering with the Sherwin Williams primer.

Definitely talk to the rep, whichever product you use.

Good luck.
TonyF

Hey, is the primer brand new or a bit older?
Could the driers in the primer have evaporated?

Have you used epoxy resin under the paint?

Have you used epoxy resin under the paint?

i previously did not even know this existed but i recently used Corotech oil base paint hardener from Benjamin Moore. It did as it says and dried faster and harder than regular oil base paint. It seems to be able to be used with any brand oil base paint. May be an option for a troublesome situation.