Can I use varnish instead of wood knotting?

[Catter]

On brand new (naked) timber garage doors, I carefully applied 3 coats, on 3 separate days, of a good quality wood knotting. Might as well have not bothered. After priming & painting in gloss, 100s of the buggers bled all over & spoiled the look. It was so frustrating. Now I need to seal some interior wood prior to painting. Should I use knotting again or would a varnish do the trick? What about clear nail varnish?

I don't use knotting. Aluminium wood primer seals knots, and is very durable, so IMO best for outdoor work. Patch prime the knots before doing the whole surface, so they have an extra coat. It dries light grey, not silver.

Resinous knots will bleed whatever you put on them if they are outdoors and the sun shines on them, even more so if they are painted in dark colours. You can encourage it out with a hot air gun and a scraper before painting or redecorating.