painting pine - seal sap?
 

I know that if you paint pine, the sap can leak through and discolor the paint.

Is there something that you can do to seal the pine before you paint (other than aging it for a year or two)?

Take a look at Zinsser products. Used to use their primer to cover smoke damage from fires.

When new wood loses moisture, and shrinks, the sap is going to be pushed out the surface.

Killz and Zinsser123 are semi-shellac(?) based i think.
They are supposed to block stains weeping through.
A rough surface is needed for them to stick. Let them dry a few days at least.

Yeah, the Zinsser. But only use the oil based NOT the water based. The water based doesn't work.

Thanks, folks.

This.

Just use shellac, Zinnser makes a straight shellac that is de-waxed, it uses denatured alcohol as a solvent. This will be your best and simplest solution for a barrier coat. Also, if the pine has not been kiln dried or has only been dried at a lower temp. meaning around 130 - 145 degrees then that is what the pitch has been "set" to, so if you place it in direct sun, even after it has been finished expect the pitch to soften if it goes above that. I custom dry all my eastern white pine and bring it too 165Degrees. Hope this helps.

Who knows. If it's cheaper to dry at a lower temp, then that's probably what I've got. It's from Home Depot. It's going to be indoors.

If it's Home Depot lumber it probably has been set to about 135. The moisture content most likely left the kiln at 12-15% moisture, in order to conform with NELMA standards. Let it acclimate to its final surroundings for a week apply the shellac to the knots a couple times and scuff and paint. If possible coat both sides to keep the panel balanced, meaning allowing ambient moisture to enter and leave the wood at an even rate on both sides.

Thanks

Dissolve and wipe away as much as you can first. A throw away clothes iron is good. I keep one in the shop to raise dents in wood with a wet rag.