Covering old knotts with Zinsser Bin

[Ambernewbie]

Morning all
Little advice please would be great.
I am decorating a lounge and we have knots showing through the white paint. I have hears that Zinsser Bin is good for covering and blocking the staining from knots.
Would I have to remove all the white satin gloss from the knots or would I be able to paint over the white paint and will this then stop the knots from showing through?
Advice will be gratefully received.
Thank you

 

[opps]

BIN is shellac based- knotting solution is shellac.

I would just apply the BIN over the painted knots.

If any of the knots are weeping sap/glue, you may need to drill them out.

 

[Ambernewbie]

BIN is shellac based- knotting solution is shellac.

I would just apply the BIN over the painted knots.

If any of the knots are weeping sap/glue, you may need to drill them out.

I dont know whether the knots are weeping heavily but I do not think i would be able to drill them out as some of the stains are quite large?

 

[slawit]

The reason the knots are seeping through is the original paint is water based, as is the sap. We never used to have this problem back in the day when we were all happy using oil based paints. You should be able to get away with using a blocker direly over the paint as long as it isn’t flaking or loose. Just give it a light sand to get a key. The Bin (red can) is a good product just don’t try an apply it too heavy 2 light coats are fair better than one heavy coat (also make sure you stir in the sediment from the bottom of the can). This will also prevent a ‘lump’ from showing through the final coat which is something you need to be careful of. A very light sanding of the Bin to feather out the edges will be needed just don’t sand too much or you’re back to square one.

 

[opps]

The reason the knots are seeping through is the original paint is water based, as is the sap. We never used to have this problem back in the day when we were all happy using oil based paints. You should be able to get away with using a blocker direly over the paint as long as it isn’t flaking or loose. Just give it a light sand to get a key. The Bin (red can) is a good product just don’t try an apply it too heavy 2 light coats are fair better than one heavy coat (also make sure you stir in the sediment from the bottom of the can). This will also prevent a ‘lump’ from showing through the final coat which is something you need to be careful of. A very light sanding of the Bin to feather out the edges will be needed just don’t sand too much or you’re back to square one.

Knots are able to weep through oil based paints. As a decorator, I still use oil based eggshell unless the customer specifies a waterbased finish (which I then use charge them extra to apply).

I suspect that fewer visible knot stains back in the "olden" days was down to the fact that timber was slown ground and dried naturally. Now, much of our timber is fast grown and kiln dried. Additionally, old school carpenters used shellac knotting solution.

Last year, I ordered door stops for 4 doors that I was fitting for a customer. The knots leaked all over the new laminate floor that I had recently fitted. I had to use white spirit to clean the floor and then drilled the knots out.