One of the most unexpected yet annoying problems with decks is how to stop sap from coming out of wood. Yes, you heard that right – that sticky mass you see when you cut wood can actually start coming out of your deck or wood furniture.

No one wants that, and luckily, there are ways to fix and even prevent this problem. This article will explore those ways and consider other essential issues relating to how to stop sap coming out of wood.

Let’s get started!

How to Stop Sap from Coming Out of Wood

The first step is to crystallize the sap bleeding from the wood if it hasn’t already crystallized. For solid masses, use a chisel or putty knife to remove. For liquid masses, dissolve and remove with turpentine. After thoroughly cleaning the wood surface, sand, stain, and apply an appropriate sealer, usually shellac-based or waterproof sealers.

Why Is Sap Coming Out of Wood Surface?

Tree sap comes out of wood that has not been adequately dried. When fresh woods are cut, they are usually kiln-dried or air-dried.

If improperly dried or green wood is used for any furniture or deck, the sap gets stuck inside the wood and may emerge when the conditions are right.

The conditions, in this case, refer to hot temperatures, either from the sun or a heat gun. This will cause the sap to melt, seep out of the wood, and solidify to the annoying mass we see.

Do you want to stain your wood while still wet, here a guide on green stain on wood to help you out.

Tools and Materials

Below are some of the necessary tools and materials to stop sap from coming out of wood.

  • Heat gun
  • Putty knife
  • Chisel
  • Mineral spirits
  • Turpentine
  • Coarse sponge
  • Clean cloth
  • Sandpaper
  • Sealer

How to Stop Sap from Coming Out of Wood

When the wood is just freshly-cut, proper kiln-drying can stop tree sap from coming out of the wood. You do not have this luxury with household wood.

However, you can fix the problem by sealing the wood surface. We will examine the steps to achieve this below and also show you how to stop sap from coming out of wood.

Crystallize the Sap with a Heat Gun

Before you get to the actual removal of the sap, you need to ensure all the sap oozing from the wood is in a state where it can be easily removed from the wood surface, which is dry and brittle.

If the sap has not fully dried and hardened, that is, still sticky or moist, it won’t be easy to clean. Any attempt at cleaning may even worsen matters, smearing the sap thin over the wood surface.

Crystallizing is a way of hardening the tree sap, making it easy to remove. To achieve this desired state, you need a heat gun. Some saps and wood can tolerate higher temperatures and drying times.

Ensure you know the type of wood you are dealing with before blasting with heat. To be safe, you can start heating at 120-140°F before slowly working your way up if the wood can handle the heat and the sap is only slowly hardening.

Remove Sap Crystals

After the sap is crystallized, you need to clean off all of it from the wood. This can be done by removing sap crystals with your hands, especially for larger sap crystal masses.

However, it is trickier when the sap crystals are small or so tightly attached to the wood surface. If using your hands to remove doesn’t work, you can use a putty knife or a chisel. You have to be careful not to dig into the wood, defacing it.

Clean off All the Sap on the Wood Surface

After removing the solid crystal masses, the next stage is looking for liquid residuals. This is a common problem if the tree sap has not totally crystallized or still coming out of the wood as a liquid.

Here, the best chemical you can use for the removal is turpentine because it will not alter the integrity and quality of the wood.

Alternatives include alcohol and alcohol-based products (an example is hand sanitizer), varnish, polish, wax removals, and mineral spirits.

  1. To actually remove the liquid residuals, the necessary steps are as follows.
  2. Apply the solvent to the affected areas of the wood.
  3. Let the solvent act on the wood for a few minutes, and then scrape the residuals with a coarse sponge.
  4. After scraping, dampen a clean cloth with some more of the chemicals and thoroughly clean the affected areas.
  5. Allow the wood dry.

Sand and Clean

When you have thoroughly cleaned the wood of sap, you need to seal the affected surfaces. However, before sealing, it is vital to sand the areas that will be sealed properly.

Note that you should only start sanding after cleaning the wooden surface. A common mistake people make is to sand before removing the sap resin masses on the wood surface.

If you trod that route, there is a high probability of the sap quickly turning to gum, which will stick solidly to the wood surface and make further removal difficult.

Sanding is not only crucial in preparing the wood for sealing but also for ridding the wood surfaces or scratches and marks that may result during the cleaning phase with putty knives and chisels.

You can start sanding with coarser sandpaper before working your way up to finer ones like the 240-grit sandpaper.

After sanding, clean the wood surface thoroughly with a clean cloth. You can use a vacuum for extensive areas. Just make sure you don’t apply a sealer on a dusty surface.


All of the previous steps only build up to sealing. Without sealing, even after the wood surface is thoroughly cleaned of the sap bleeding from it, the same can happen again.

This is because you have only treated the symptoms, not addressed the root cause.

The steps to follow for proper wood sealing are outlined below.

Step 1: Choose the right sealer. Usually, shellac-based sealers are the go-to option to stop sap oozing from wood.

Step 2: Identify the areas where sap is likely to come out, usually the knot areas.

Step 3: You can stain the surface before sealing. In fact, you can choose to stain instead of seal in some less-exerting regions like cold and humid climates. However, this method is not as fool-proof as sealing. Staining before you seal can improve the quality of the final seal.

Step 4: Seal the wood by applying multiple layers of the sealer on the affected areas and other areas likely to exude sap in the future.

What Types of Wood Have More Sap?

Some wood types have been identified to exude more sap than others. These include:

Fresh wood

This comes as little surprise, really. This wood type is rich in sap, and it may not take more than a few days for sap to start oozing out of the surface.

Untreated wood

Typically, woods are chemically treated before using them. This doesn’t only function to keep sap coming from the wood but also to prevent degradation and microbial attack.

You shouldn’t do this yourself if you’re not an expert. You must also use rubber gloves when handling chemicals.

Poorly dried wood

Not drying wood properly or at all can increase the sap that oozes out of the wood. Kiln-drying and air-drying are the two typical drying formats.

Woods have to be completely dry before they can be used to prevent sap from getting stuck in them and melting later.


How to remove sap from finished wood

To remove sap from finished wood, first, crystallize the sap to harden it. The goal is to get dry and brittle sap masses. Upon completing the wood crystallization process, you can remove big masses with your hand and small masses with a putty knife or a chisel. For liquid residuals, use turpentine or mineral spirit to remove.

How to stop sap coming out of painted wood

The first step is to crystallize the sap bleeding from the wood if it hasn’t already crystallized. For solid masses, use a chisel to remove them. For liquid masses, dissolve and remove with turpentine. Also, painting painted wood can help reduce the occurrence of sap coming out of painted wood, but it may not completely stop it in all cases. After cleaning the wood surface, sand, stain and apply shellac-based or waterproof sealers.

How to paint over wood sap

Paint is one of the alternative measures to stop sap seeping from wood. This is because the paint film is impervious to the sap. You can apply your paint over the sap using a brush after preparing your paint. Do not paint over solid masses of sap; rather, clean the sap off before applying paint.

How to clean sap off wood

Dampen a clean cloth in turpentine or hand sanitizer and clean the surface of the wood. Ensure the cloth used is clean to avoid marks and scratches on the wood surface. Also, after cleaning with these chemicals, ensure you allow the wood to dry before continuing work on it.

How to remove sap from painted wood

Removing sap from painted wood is not nearly as easy with unpainted wood because the sap rarely breaks the paint film. Instead, sap pushes the film up, totally disfiguring the wood. For proper removal, you need first to strip the paint film using paint strippers. After this is done, the sap can be crystallized and then removed. Sanding is usually necessary before reapplying paint.

Will polyurethane seal sap?

Polyurethane is a common wood finish and can be used as a sealer for sap. Because several coats are applied to beautify and toughen the wood surface, there is little chance of sap breaking the film. However, the polyurethane coat may get disfigured after a while, especially in woods with a heavy amount of sap oozing out.

How to remove sap from wood deck

To remove sap from an outdoor deck, crystallize the sap to harden it using a heat gun. After crystallization, you can remove big masses with your hand and small masses with a putty knife or a chisel. For liquid sap residue, use mineral spirit to remove it. Apply a sealer over the wood deck, paying more attention to knot areas that are more likely to exude sap.

Why is sap coming out of my deck boards?

Sap can come out of your deck board if the wood was not properly dried or chemically treated before it was used. Also, if the wood is constantly exposed to hot temperatures and direct sunlight, sap may begin to come out of it.

Can you paint over tree sap?

Yes, you absolutely can. While this isn’t the best approach, you may be able to pull it off in cold environments where there is little worry about the sap melting and bleeding out. However, note that sap from trees cannot penetrate the paint and will only push the paint film up, totally disfiguring the wood surface.

How do you remove sap from wood before staining?

It is crucial to remove sap before you stain the wood. Start by crystallizing the sap to harden it and then remove it with a chisel or a putty knife. For liquid residuals, use turpentine or mineral spirit to remove. All of the sap has to be removed before staining.

How to remove pine sap from wood

Pine sap can be removed by crystallizing the sap with a heat gun and then removing the dry and brittle masses. For liquid residuals, turpentine and mineral spirits can be used. After proper removal, a polyurethane coat can be applied over the wood surface.

How to stop sap from coming out of deck boards

Sealing is the best approach to stopping sap exuding from deck boards. First, remove sap from the deck board, clean the surface, and sand. After obtaining a smooth surface, apply an appropriate sealer to the deck board, particularly to knot areas.

Can you seal in sap?

Yes, you can seal in sap. This is done after properly removing sap masses either by crystallizing them or using a chemical solvent. Sand the wood and then apply a shellac-based sealer to seal the wood surface.

Also check out: Is bleach an effective wood rot stopper?


Sap is a natural exudate from all trees. Under hot temperature conditions, the sap can ooze out of the wood surface. To stop this, you need to seal the wood surface. This is done by cleaning the wood of sap, sanding it, and then applying the sealer.

Shellac and waterproof sealers are usually the best options for proper sealing. To prevent sap from seeping out at all, ensure you only use properly kiln-dried and treated wood.

2 thoughts on “How to Stop Sap from Coming Out of Wood”

  1. I had a new deck installed last year. The used walminzed pine. It must not have been put through a complete dry process because all the knots in the boards bleed sap badly in the hot sun. What can I do to stop it. What is the best sealer to use.


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