How can I remove sap from lumber?

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Forum topic by NickyP posted 09-10-2013 10:02 PM 5874 views 0 times favorited 10 replies Add to Favorites Watch
View NickyP's profile


151 posts in 760 days

09-10-2013 10:02 PM

Topic tags/keywords: question trick tip

Long story short: I have milled down and squared up 2×4’s into legs for an outdoor table. After glue up, one of the legs oozed out a good stream of sap from a knot hole. I’d like to remove this sap prior to staining and finishing the table. Does anyone have a good solution?

-- -- "Never underestimate the power of a kind word, a good deed, or a table saw."

10 replies so far

View DrDirt's profile


3509 posts in 2779 days

#1 posted 09-10-2013 10:06 PM

Scrape the excess

Wipe down with lacquer thinner.

Seal with shellac, and use a gel stain.

Good luck – I don’t usually do any finishing with color on construction lumber.
Either a clear finish or I am painting it – never tried to stain.

-- “The kind of man who wants the government to adopt and enforce his ideas is always the kind of man whose ideas are idiotic.” ― H.L. Mencken, Minority Report

View Bill Davis's profile

Bill Davis

226 posts in 2961 days

#2 posted 09-10-2013 11:40 PM

Here’s a quote from Fine Wood Working magazine:

“Here’s how I got around the sap problem:
I began by scrubbing off as much of the sticky stuff as possible using rags and mineral spirits. Then, I cut off as much of the sappy edge grain as possible at the bandsaw and rough-cut my smaller components to size. From there, it was just a matter of baking the wood until the sugary sap crystalized and then hardened. I baked the pine at 160-degrees for a little over an hour—keeping a close eye on the oven for safety reasons. I found that the high temperature actually did two things: 1) it drove most of the sap up to the surface, where I could easily remove it with hand tools, and 2) it hardened any sap left behind in the wood, thus preventing possible “weeping” through my final finish in the future. In the photo at left, you can clearly see how the sap migrated to the surface, particularly via the end grain.

View gfadvm's profile


13750 posts in 1727 days

#3 posted 09-11-2013 01:07 AM

Mineral spirits works well to clean pine sap off my tools and hands so should work on wood.

Shellac will seal that sap very well and prevent bleed through.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View WDHLT15's profile


1404 posts in 1512 days

#4 posted 09-11-2013 01:30 AM

In trees prone to sap, like conifers, the sap has to be “set” by heating up the wood to a temperature above the highest temperature that the wood will see in use. This done during the kiln drying process. Air dried wood does not have the sap “set”.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln.

View NickyP's profile


151 posts in 760 days

#5 posted 09-12-2013 11:10 AM

I ended up scrapping off excess with a paint scraper followed by wiping it down with mineral spirits and sanded to a smooth finish. Worked great! Thank you all for your advice.

-- -- "Never underestimate the power of a kind word, a good deed, or a table saw."

View Nomad62's profile


726 posts in 1995 days

#6 posted 09-17-2013 04:20 PM

Bills advice is best, in my opinion; the wood will continue to leak sap any time it gets warm/warmer than before, until it is almost empty which will take a long time. Best to heat it to 160, but well beyond its typical potential environment should be ok.

-- Power tools put us ahead of the monkeys

View Marcio Wilges's profile

Marcio Wilges

22 posts in 334 days

#7 posted 11-21-2014 06:50 AM

I’m feeling very lucky that I stumbled on this thread before trying my hand out at my wood. It really pays to read around huh! I would never have given a thought to sap removal before today to be honest. Can anyone actually just share with me what the difference is with leaving it there as opposed to having it all scraped away?

-- Marcio Wilges @

View bold1's profile


210 posts in 884 days

#8 posted 11-21-2014 02:57 PM

We usually take White Pine to 180 F. to set the sap. The longer it’s kept there the more the wood seems to become brittle for working, even when steamed to relieve the stress. Marcio, anyone getting against the wet sap is going to stick fast to anything. And sap is hard to seal in. As the wood expands and contracts it “bleeds” thru most finish/sealers. It’s the worst around knots, but can be in pockets other places in the wood. That’s why we heat it to “bake” it solid. It will stabilize in air dried, but can take many years.

View Rob's profile


1 post in 1275 days

#9 posted 03-09-2015 05:38 PM

I recently built 2 beautiful Adirondack chairs from mélèze (larch).
2 coats of Cetol primer followed by 3 coats of Cetol outdoor wood stain.
Four months later I’ve got sap bubbles all over the back.
I can’t put the chairs in the oven so I need another solution.
Any suggestions very much appreciated.

View pjr1's profile


26 posts in 251 days

#10 posted 03-09-2015 09:05 PM

Rob it could be a problem this time of year depending on where you live but have you considered some sort of solar oven? Shouldn’t be difficult at all to obtain 160-180 degree temps with a clever set up.

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