How to paint over knots

[redhexagonal]

So I have a staircase that is painted in yellowing white gloss, and covered in stains where knots have come through.
I am planning to paint it with grey Dulux Satinwood which is oil based. How should I get rid of these knot stains for good before I paint over them? I heard Zissner B-I-N is good? Then what prep do I need before I apply the topcoat, is sanding the gloss enough or do I need an undercoat too?

 

[JohnD]

if there are a lot, Aluminium Wood Primer (which dries grey, not silver) will seal them and prime the whole piece.

If very resinous, a hot air gun will boil out the resin, which you can scrape off when bubbling so it is not reabsorbed. Traces left on the surface will harden like varnish when cold and you can sand it off. Do this before the rest of your prep work.

 

[redhexagonal]

if there are a lot, Aluminium Wood Primer (which dries grey, not silver) will seal them and prime the whole piece.

If very resinous, a hot air gun will boil out the resin, which you can scrape off when bubbling so it is not reabsorbed. Traces left on the surface will harden like varnish when cold and you can sand it off. Do this before the rest of your prep work.

Yes there are alot. Is aluminium based primer preferable to Zinnser B-I-N? Would I just spot prime the knots?

 

[JohnD]

I use it, especially on resinous and outdoor wood (it is very durable). You paint it over the whole thing, rather than patches. I haven't used BIN so I can't compare.

 

[redhexagonal]

Yes there are alot. Is aluminium based primer preferable to Zinnser B-I-N?

I use it, especially on resinous and outdoor wood (it is very durable). You paint it over the whole thing, rather than patches. I haven't used BIN so I can't compare.

does that mean I’d have to sand all the gloss back to bare wood?

 

[JohnD]

that would be a better job, especially if there are lots of knots and you miss some, but you can do patches if you want. You will need to apply undercoat and sand lighly to level the surface if you are doing patches.

A hot air gun will be quicker and cleaner than sanding. And not as noisy.

 

[redhexagonal]

that would be a better job, especially if there are lots of knots and you miss some, but you can do patches if you want. You will need to apply undercoat and sand lighly to level the surface if you are doing patches.

A hot air gun will be quicker and cleaner than sanding. And not as noisy.

Would paint stripper work?

 

[JohnD]

I don't find modern strippers much good.

Wait a while, there will be some pro decorators in later.