Joe90":3rrodxu9 said:
Hi
I'm wondering if knots will bleed through the top coat if I spray pine furniture using AC tinted lacquers...Any help would be appreciated.
Cheers Joe
You're right to be concerned about resin bleed through of knots, particularly on resinous softwoods like pine.
However, you mention that you have already used Zinnser's Bin primer. This is a shellac based product. Shellac is a traditional sealer for 'difficult' woods, e.g., knotty stuff. For instance, a traditional primer to use on painted wood is knotting. It's a brown sealer made of shellac and the idea is you primarily spot paint it over the knots. Over the top of that goes the rest of the paint.
Whilst shellac is very good for preventing the bleed through it's not infallible, and this is because some knots are more resinous than others. This is a result of two factors, ie, how resinous the tree and its knots is/are in the first place, and how the wood was dried. Pine dried for construction use is not dried to a particularly low MC, usually about 15-16% MC, nor does it go through such a high temperature cycle during part of the kilning process as pine dried for furniture grade use. Pine dried for furniture use is usually dried to about 8% or 10% MC in the UK, and the high temperature cycle 'cooks' the resin to set it hard. Hard resin doesn't bleed, but this hot cycle in the kiln doesn't always fix all the resin.
Anyway, enough of that stuff and a look at the lacquers. AC lacquers in common with all the nitro-cellulose family are their own sealer. In other words an AC or nitro-cellulose sanding sealer or primer is not required. You can use one if you like and they do have some advantages, particularly in a high production environment, but for one off work they aren't needed.
However, shellac is a universal primer and, specifically, de-waxed shellac can be used underneath any other film forming polish-- the de-waxed bit is especially important underneath water based finishes because these will not adhere well to normal shellac which naturally has wax in it.
So, in this case if you've sealed the wood with the Zinnser primer you can spray over the top of that with your tinted Morrell's AC lacquer. Resin bleed through will in large part be determined by the factors I described above, eg, is you project made of construction grade wood or furniture grade wood, and how naturally resinous is it? Slainte.
