How to Stop Timber from Bleeding Through Paint
If you've painted bare timber in a light colour and then watched brownish or yellowish marks come up through it a few days later, that's tannin. It's a natural compound in some timbers that dissolves in the water in fresh paint and travels up through the film as it dries, and it's at its worst around knots and under white.
Why another coat won't fix it
Painting over it again with the same water-based paint just gives the tannin more water to travel in, so it comes back through the new coat as well. What stops it is a stain-blocking prepcoat underneath, which puts a barrier between the timber and your topcoat so the tannin has nowhere to go.
Get the timber ready first
Sand the timber smooth and dust it off properly, because a prepcoat bonds to clean timber and not to sanding dust. On older timber that's been handled a lot, wash any grease off with sugar soap and let it dry right through before you start.
Use a stain-blocking prepcoat
Haymes makes more than one prepcoat and they're built for different jobs, so tell us it's for tannin when you come in and we'll make sure you walk out with the right tin. Read the tin as well, because it lists the surfaces that prepcoat is made for. Spot prime the knots first if they're the worst of it, then do the whole surface.
Give it the full recoat time
Let the prepcoat dry for the full recoat time on the tin before your topcoat goes on, because going over it too early can drag the tannin up into the new paint anyway. If a mark still shows once it's dry, a second coat of prepcoat on that spot will usually seal it.
Outside timber
On weatherboards and verandah posts the same rule applies, and it's worth sorting out whatever is letting water into the timber first, because damp timber keeps feeding tannin to the surface.
Shop related products
- Paint Brush Utility 100mm Synthetic. For spot priming knots and cutting in.
- Unifiber 230mm Roller Kit, 11mm nap. For the broad flat runs of timber.
- Phoenix 230mm Plastic Paint Tray. It takes the 230mm roller cover.
- Uni-Pro Canvas Drop Cloth 1.5m x 3.6m. Catches the drips under trims and posts.
Did you know the Haymes prepcoats are in the shop only, because paint is classed as dangerous goods and can't be posted. We keep Ultralock, Ultrahold, Ultracover and Ultraseal across the common sizes, so give us a ring on (08) 8536 4333 to check what's on the shelf.
We mix and tint to order in the shop from the Haymes and Taubmans range we stock, and there's more on the paint mixing page. The brushes and rollers that are online sit in paint and accessories.
Read next
- Do you need a primer, and which Haymes prepcoat
- Haymes Ultrahold, the stain blocker and when you need one
- How to sand a wall properly before you paint
White paint and I have an understanding, and the understanding is that I prep first.
Candeece
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