Tannin Bleed on Wood: Causes, Fixes and How to Stop It
Tannin bleed is the yellow, tan or brown staining that rises from bare or old timber and shows through your paint. It is caused by natural compounds in the wood, carried to the surface by moisture. The fix is to remove the stain, let the wood dry fully, then seal it with a proper stain-blocking primer before you repaint. Another coat of the same topcoat will not cure it.
Below, we explain why it happens, which woods are the worst offenders, how to deal with knots, and what a tradesperson does differently to stop it coming back.
TL;DR
Tannin bleed is brown or yellow discolouration that migrates from the timber through the paint film, and it is most obvious on white and pale colours.
Water is the carrier. Fix any damp or leak first, then dry the wood completely before priming.
Clean off existing stains, then seal with a stain-blocking primer (oil-based, shellac-based or a specialist tannin-blocking primer). Heavy staining may need two coats.
Knots need their own treatment: heat, scrape and seal before priming the whole surface.
Skipping the primer is the most common reason stains return within days or weeks.
Table of Contents
What tannin bleed actually is
Timber is not inert. Many species contain tannins and other water-soluble extractives, and when moisture gets into or onto the surface, it can dissolve them and pull them outward. Sherwin-Williams describes tannin bleed as brownish discolouration on the paint surface caused by tannins migrating from the wood through the paint film, either as they rise or when water carries staining substances to the film later.
The look is distinctive. Dunn-Edwards notes that it usually appears as yellow or brown stains, especially under lighter colours, and that it is common in the first year after painting new wood. A fresh white door with tea-coloured streaks following the grain is the classic case.
It is not a sign that the wood is rotten or damaged. It is a chemistry problem between the timber, the water and the coating you chose.
Which woods cause it most
Some timbers are far more likely to bleed than others. Cabot’s technical bulletin calls them “staining woods”: woods containing tannic acid and other water-soluble extractives, with western red cedar, eastern white cedar, redwood, mahogany and ipe named as popular examples.
In UK homes, the timbers we most often see causing trouble are:
Cedar and redwood, common in cladding, fascias, sheds and garden structures.
Mahogany and other hardwoods, often found in older window frames, doors and staircases.
Pine with live knots, where resin as well as tannin can stain the finish. Resin is a separate issue, covered below.
New or freshly exposed timber, including replacement window reveals and joinery, where the extractives have not yet weathered out.
If you are not sure what species you have, treat it as a bleeder. A stain-blocking primer costs little compared with repainting a whole room or elevation twice.
Why it comes back after you repaint
The most frustrating thing about tannin bleed is that a second topcoat looks perfect for a few days and then the stain reappears. That happens because ordinary paint, particularly water-based paint, does not stop the tannins moving. It simply sits on top of them.
Water is the key. Cabot’s bulletin frames extractive bleeding as not necessarily a coating failure, but as moisture and extractives moving under sun and pressure, which is why moisture management and correct sealing are the main remedies. Dulux Trade’s primer data sheet makes a similar point: when you block stains caused by water or damp, the original cause must be rectified.
In practice, that means checking for:
Leaking gutters or failed flashing wetting fascias and soffits.
Condensation or damp around window reveals and sills.
Cracked or missing sealant at joints.
Persistent damp in bathrooms or kitchens. Our guide to damp-proofing painting covers this in more detail.
Paint a stain-blocking primer over a wall that is still wet and you are only delaying the next stain.
How to get rid of tannin bleed that has already appeared
The order matters. The sequence below follows manufacturer guidance and is the same logic a professional decorator works through.
1. Find and fix the moisture source
Nothing else will hold until the wood stops getting wet. Repair the leak, clear the gutter, reseal the joint.
2. Scrape off loose or flaking paint
Stained paint that is failing needs to come off back to sound edges. Sand lightly to feather the edges and give the primer something to grip.
3. Remove the visible staining
Dunn-Edwards advises removing visible stains with oxalic acid or an oxalic-based cleaner, then rinsing. Oxalic products are hazardous, so follow the label on gloves, eye protection and ventilation.
For surface contamination of natural timber such as tannins, gums and oils, Dulux Trade’s preparation guidance is to wipe with a cloth dampened in a suitable solvent, and specifically not white spirit or turps. Check the solvent recommended by your primer’s manufacturer.
4. Let the wood dry completely
Dunn-Edwards recommends allowing the surface to dry for at least 48 hours, depending on the weather. In a damp British November, allow longer. Painting too early traps moisture, which then pushes tannins straight back up.
5. Prime with a stain-blocking primer
This is the step that decides the result. We cover your options in the next section. For heavy staining, two coats of primer is the recommended approach.
6. Topcoat
Once the primer has cured, apply your colour in the number of coats the manufacturer specifies. Our short guide to what primer does in decorating explains why this layer cannot be skipped.
Can you paint over tannin bleed?
Yes, but only if you seal it first. Painting straight over the stain with another coat of emulsion or water-based gloss usually gives you a few good days and then the stain again.
The sealing options fall into three groups.
Primer type | How it works | Where it suits |
Oil/alkyd-based stain-blocking primer | Forms a film that traps tannins; Sherwin-Williams advises an alkyd or oil primer, or a coating designed to trap tannins | Exterior joinery, cladding, fascias, window frames |
Shellac-based primer | Alcohol-based and dries to a dense, non-porous film that locks in contaminants and stops them reaching the topcoat | Knots, interior stains, severe or recurring bleed |
Water-based tannin-blocking primer | Specially formulated to block tannin while keeping a low-odour, quick-drying system | Interior joinery, softwood, pine and plywood where fast turnaround matters |
Water-based specialist primers
Some modern water-based primers are made for this job. Dulux Trade’s Aqua UniPrimer states that it can block tannin bleed, is touch dry in 30 minutes and can be recoated after one hour, with one or two coats of a suitable topcoat on top. Thorndown’s stain-blocking primer is described as multi-surface for tannin and stain blocking on timber including pine, cedar, redwood and plywood, and the maker notes a second coat may be needed on very knotty or high-bleed wood.
The lesson from both is the same: a primer that is explicitly rated for tannin blocking is not interchangeable with a general-purpose undercoat.
Shellac primers
Shellac is the heavy hitter. Because it is alcohol-based, it forms a barrier rather than dissolving the staining compounds, and Rawlins Paints says that barrier is why it can outperform standard primers when tannins keep reappearing. It is the same logic we use for nicotine stains under a shellac primer and for bleed-through on smoke-damaged walls.
Shellac gives off strong fumes and dries fast, so ventilate well and work in manageable sections.
Knots, resin and the knotty pine makeover
Knots are a slightly different problem. Tikkurila explains that knots bleed because resins seep to the surface and cause discolouration, and that stopping this resin is challenging. You see it as a yellow or brown ring around each knot, often within days.
If you are planning a knotty pine makeover, such as repainting pine panelling, doors, skirting or a kitchen, the knots are where the work is.
How to treat knots before painting
Check the knot type. Dulux Trade’s advice for live knots is to play a hot air gun over them to draw out resin, scrape the resin off, then degrease. Dead knots should be removed and filled with a suitable woodfiller.
Scrape, heat, scrape again. Tikkurila’s suggested procedure includes scraping away excess resin, heating the knots, scraping again, washing oily surfaces down with cellulose thinner and allowing the timber to settle before priming.
Seal each knot. Rawlins notes that two thin coats of shellac on each knot usually stop brown rings reappearing through emulsion within days.
Prime the whole surface. Farrow & Ball says to lightly sand bare wood for adhesion and, where needed, patch prime knotty or resinous woods with a wood primer and undercoat.
Respect drying times. For their system, a minimum of four hours between coats is advised. Always follow the maker’s recoat times for whichever product you use.
Heat and colour make knots worse
Teknos points out that resin bleeding is more likely on south-facing elevations and on dark surfaces, where the sun’s heat liquefies the resin and pushes it to the surface. It also says that water-based coatings are more likely to let resin through because of their relatively high moisture vapour permeability.
So if you are painting a sunny pine porch a dark colour with a water-based finish, expect the knots to try to push through, and put extra care into the knot sealing.
If what you actually want is an aged, character look on timber rather than a clean opaque finish, a distressed wood finish recipe can be a good way to treat stained boards, though bleed-prone wood still needs sealing first.
Interior or exterior: what changes
Interior joinery such as doors, skirting, staircases and kitchen cabinetry usually bleeds because of knots, new softwood, or moisture from bathrooms and kitchens. A shellac or specialist tannin-blocking primer, a proper clean, and a smooth topcoat do the job. If you are respraying kitchen doors, grease removal matters too, and our guide on cleaning kitchen doors before painting explains how.
Exterior timber has the added challenge of weather. Rain, dew and sun cycles keep driving moisture in and out. Cladding, fascias and window frames need dry weather, thorough drying time, and a primer and topcoat system suited to external use. If it rains soon after you finish, see what rain after exterior painting does to a fresh coat.
Common mistakes that bring the stain back
Using a general undercoat instead of a stain-blocker. Not all primers block tannins.
Painting damp wood. Moisture is the delivery system.
Skipping the knots. Even a perfectly primed board will show brown rings from unsealed knots.
Applying one thin coat over heavy staining. Where bleed is heavy, plan on two coats of primer.
Ignoring the cause. Blocking a stain that a leak is feeding only buys time.
Rushing between coats. Follow the stated recoat times, particularly in cold or damp weather.
For a wider look at what a primer is doing under your paint, our homeowner’s guide to paint primers and our explainer on wall priming are worth a read.
Our perspective
We see tannin bleed most often on jobs where the paint was fine and the preparation was rushed. A homeowner repaints a pine door or a set of window reveals, it looks great for a week, and then the tea-coloured marks arrive. The answer is almost never more paint. It is a better sequence: sort the moisture, clean, let the timber dry, seal the knots, and use a primer designed to block stains. That is why we are patient with prep. As a family-run business, we would rather spend the time up front than come back to a job. We also use advanced spraying techniques, including airless spraying, which can give a smooth, even coat of primer and topcoat across joinery, cladding and kitchen doors, and we aim for finishes that last. If you have a stubborn stain that keeps returning, we are happy to look at the wood, work out whether moisture or the timber itself is behind it, and recommend the right system. Angus
Want it sealed and painted properly?
If you would rather not spend a weekend scraping knots and waiting on primer, our team handles it for homes and commercial properties across Cornwall and the South West. We prepare the timber, block the stains and finish with the coating system the job needs, whether that is interior woodwork, exterior joinery or cladding. Take a look at our domestic painting service, or our exterior home painting for fascias, frames and cladding.
For kitchen doors, bathrooms and fine woodwork finishes, see our interior and spraying services, or get in touch to talk through your project and request a quotation.
FAQ
How do you get rid of tannin bleed?
Fix the moisture source, scrape off loose paint, and clean the stain with an oxalic-based cleaner, then rinse. Let the wood dry for at least 48 hours, longer in damp weather. Then prime with a stain-blocking primer, using two coats for heavy staining, before your topcoat.
Which woods have high tannin content?
Western red cedar, eastern white cedar, redwood, mahogany and ipe are commonly named as staining woods. Oak is also well known for tannin content. Pine tends to cause trouble through knots and resin rather than tannin alone.
Can you paint over tannin bleed?
Yes, as long as you seal it first. Painting over it with ordinary paint usually leads to the stain reappearing. Use an oil-based, shellac-based or specifically tannin-blocking primer once the wood is clean and fully dry.
Why do knots bleed through paint?
Resin in live knots moves to the surface, particularly when warmed by the sun, and discolours the paint. Heat and scrape the resin, seal each knot with shellac or a suitable knotting product, then prime the whole board before painting.
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