Sappy Situation

[Mike Ontko]

I'm in the process of building a bookcase using cherry and CVG Douglas fir, based on plans from a corresponding article in FWW #161. I'd made up the fir panels a couple of weeks ago and have had them sitting in my insulated attached garage shop just waiting until I can finish the cherry frame. Ambient temperatures in my shop have risen enough in this time that a small cavity (what I thought was just a blemish) opened up on a one of my bookcase side panels, creating a 1-1/2" blob of sap on the surface. That blob is on both of the side panels because they happened to have been leaning against each other. The wood is still bare and unfinished.

Will I be able to remove that sap and then seal the area around that sap fissure so the panel can be finished with multiple coats of either a Danish or tung oil?

I've read one post on this board that recommended naptha, but that seems like it might be too harsh on the wood and possibly affect the finish.

[Mike Ontko]

Pics:

ForumRunner_20160326_083931.jpg. ForumRunner_20160326_083941.jpg

[Cody Colston]

Evidently the Fir was not kiln dried or at least not at a high enough temperature to set the sap. Once the temperature rises even higher, the sap will again want to seep, even with an oil finish over it.

I'd probably use something like Naptha to clean up the sap that has aready seeped out. I don't think it will do anything bad to the wood. As for sealing it in, Shellac is your best bet. I've never tried Danish oil over shellac so I can't speculate how it would turn out.

[Steve Peterson]

What temperature and duration would be required to set the sap?

Douglas Fir is the primary framing lumber out here in the west. Every attic I have been in has a fair number of trusses with fairly significant sap leakage, but they appear to be stabilized. Summer temperatures usually reach the low 100s about 10-15 days per year. I suspect that the temperature must reach 130-140 degrees in the attic. Would it be sufficient to store a few boards in the attic for a summer as a cheap way to kiln dry them?

Steve

[Jerry Miner]

I feel your pain. I've been working with Doug Fir and sap streaks for decades. The only successful "fix" I've found is to physically dig out the sap and fill the remaining void. A solvent like naptha or even paint thinner will clean up the surface sap and help clean out the sap pocket without damage to the wood or the finish--as long as you let it evaporate before applying finish.

[Mike Ontko]

The only successful "fix" I've found is to physically dig out the sap and fill the remaining void. A solvent like naptha or even paint thinner will clean up the surface sap and help clean out the sap pocket without damage to the wood or the finish--as long as you let it evaporate before applying finish.

That's what I was hoping. I may fill the void with a clear epoxy before finishing. Hopefully, this would help to seal off the possibility of any further oozing in the future.

[Cody Colston]

What temperature and duration would be required to set the sap?

Douglas Fir is the primary framing lumber out here in the west. Every attic I have been in has a fair number of trusses with fairly significant sap leakage, but they appear to be stabilized. Summer temperatures usually reach the low 100s about 10-15 days per year. I suspect that the temperature must reach 130-140 degrees in the attic. Would it be sufficient to store a few boards in the attic for a summer as a cheap way to kiln dry them?

Steve

The pitch (sap) will be set at the highest temperature the lumber reaches. I believe kilns usually heat it to 160 degrees for 24 hours. If the lumber never reaches 160 degrees again, the sap will not become liquid. I think storing the boards in the attic to set the pitch is a very good solution.

[Dave Zellers]

Torch it.

Hit that spot with a propane torch and bleed out the remaining sap. You have to be VERY careful and have a light touch or you will burn the wood. But it works. Practice on a scrap to get a feel for the best distance and how quickly you have to pull away to avoid burning. I do this every time I'm working with pine and a knot or two just can't be avoided. Bleed the sap out of the knot, wipe it clean with thinner, hit it with two coats of BIN and then finish paint- no one will ever know.

Even though you are doing a clear finish, I would still bleed it out, then following Jerry's advice I would scrape the void clean and possibly fill it with a matching sliver of fir.

[Andrew Hughes]

Pitch pockets are different than setting the sap fir.Ive had them show up in kiln dryed Vg.The interior doors in my house has them looks like they were cleans out and filled with wood.Of course back in the 50s my houses doors were considered paint grade.
I brought them to their present glory.

[Joe Calhoon]

We build a lot of VG Fir doors. Kiln drying does not set the pitch on these. They will bleed forever if not fixed. We pretty much try to avoid them but when you cannot our method is similar to Jerrys. We dig out as much as possible and fill with a product called Knot Filler. It is basically a hot melt glue clear or with color added. Epoxy works also.

[Cody Colston]

Kiln drying does not necessarily mean the pitch has been set because all kilns don't always reach the target temperature or hold it long enough to thoroughly heat the wood. If the pitch is still bleeding, I would question the kiln operator to verify how high and for how long the temperature was held.

Dr. Gene Wengert recommends 180 degrees kiln temperature for 24 hours to set the pitch. I mistakenly suggested 160 degrees in a previous post. Whether Doug Fir or SYP, it's purely a function of achieving the correct wood temperature.

[Mike Ontko]

Great info in these posts. Thanks to everyone!

I was considering using a hot air gun to force out the remaining sap, and then use a filler like epoxy to seal it off permanently. I'd like to use clear epoxy because I actually want to keep that dark streak blemish in the piece. It just hadn't occured to me that it would be filled with sap. Live and learn, I guess.

[John TenEyck]

I would take a different approach. I'd route out the offending area and glue in a piece of new wood. I might even run a dado the length of the panel and install a full strip of new wood so there would be no end grain butt joint. Done well, you'd never see it.

John

[Joe Calhoon]

Kiln drying does not necessarily mean the pitch has been set because all kilns don't always reach the target temperature or hold it long enough to thoroughly heat the wood. If the pitch is still bleeding, I would question the kiln operator to verify how high and for how long the temperature was held.

Dr. Gene Wengert recommends 180 degrees kiln temperature for 24 hours to set the pitch. I mistakenly suggested 160 degrees in a previous post. Whether Doug Fir or SYP, it's purely a function of achieving the correct wood temperature.

Cody, I think that is correct. I found this link

http://www.bcwood.com/wp-content/upl...s-Fir-Pine.pdf

We have used a lot of VG fir over the last 35 years or so and I think most of the mills do not do this corectly.
VG is usually not dried below 12%. I wonder if this is part of the problem.