This was a comment on another thread. Rather than drag it off topic this is a little of what I've learned regarding sappy wood over the years


The outer wood layer 10-15 rings deep is the sapwood. Technically the cambium is a very thin sheath covering the tree, dividing inward to form xylem, wood, and outward to form phloem the inner bark (what most people mistakenly call the cambium). The outer xylem, the sapwood, is where the sap moves upward from the roots. The phloem or inner bark is where the sugar rich sap flows back down for storage. That is the vertical transport system. The rays form the horizontal transport to feed the cambium and to access the edge of the deeper core for storage
Rays also store carbohydrates, starch. Starch is a comlex molecule formed of simple sugars.

The column of water in the xylem, from the roots to the leaves is in tension. As a molecule leaves the stoma in the leaf a molecule enters the root. The breaking of this tensile column causes an air embolism that generally signals the beginning of the end for the cells in that column and the beginning of their transformation into heartwood. As the water levels drop in the heartwood, starch can hydrolize to sugars which both while decomposing consume oxygen and produce CO2 creating pressure which further destroys the tension based water column. The byproducts of this decomposition are polyphenols, waxes, fats, tannins, resins, gums, oils, aromatic and coloring agents... the spent byproducts of respiration, the extractives.

Sap does not go down in winter, there is no pump to re-establish the water column. Flow stops in hardwoods and it seals itself through the dormant period but the moisture content remains at least the same and sometimes slightly higher. Conifers never stop, if they are not frozen they are growing albeit slowly. The needle is an adaptation for this purpose, narrow and covered by a waxy cuticle to prevent winter dessication. Freezing in hardwood causes an embolism in the water column and it cannot normally be re-established. This freeze line shows itself by species as you drive north. Conifers can bleed freezing sapwater into surrounding interstitial spaces and then reabsorb it into the cell lumens and can re-establish water column, to a point.

Resin is not sap, although we use the terms interchangeably. Resin is produced in specialized cells, epithelial cells, that lie in the interstitial spaces between the normal tracheid cells of most conifers. Resin is believed to be for helping to protect damaged tissue and to help repel invaders. The epithelium consists of longitudinal and ray cells so it has the ability to transport vertically and horizontally. Remember the heartwood is dead and blocked by extractives so there is effectively no transport there. The epithelial cells are the last to die, producing resin for up to 6 months after a tree is felled if left to naturally dry. Resin can also "flow" on any warm day in an air dried timber. I've opened up a fresh face on 160 year old pine, left it in the sun and had sticky sap bead up. Cold resin in the winter is much slower to exude and less sticky than warm sap being pumped by the epithelium in the summer. If you look at a end grain cookie that has bled count the rings of sappy wood before you get to the heartwood. This is telling you how long the average cell lives.


The gathering and processing of resin was a cottage industry in the old days. Longleaf pine was one frequently tapped tree of the early forest. In the 1830 census several of my ancestors reported "turpentine" as their occupation. In '65 Sherman, running behind schedule, illuminated his pathway into NC by lighting that pine forest and marching by its torchlight.
Micrograph of a resin duct;
http://www.botgard.ucla.edu/html/botanytextbooks/generalbotany/barkfeatures/a1438tx.html

Some Wiki definitions;
http://en.wikipedia.org/wiki/Polyphenol
http://en.wikipedia.org/wiki/Starch

Don, I have tipped balsam fir for Christmas wreaths for many years, we used to test the tip of the branch, at the new bud, if it was wax coated it was ready to start the season. This meant the needles were set and would not fall out through the holiday season. If pinched the wax would crack apart.

I am now working some White Pine and it is very sticky, we are using turpentine for clean up of tools and the work surface. I am expecting that a wipe and scrape system of turp' will suffice for the weeping in that layer. Will it come back in all it's glory after this treatment? Time will tell. Any experience and comments? I have been using olive oil as a clean up on hands, even rubbing some on your hands before work makes cleaning the hands easier. Clothes are another issue and the zipper on my winter jacket is hard to start due to the pitch.

Thanks for the informative post.

Tim

Tim

That is an informative post.

I often wonder how trees can survive in a freezing environment in winter, if, as you say, they remain at least as hydrated as in summer. Don't evergreens have a unique ability to live even though their cells "fracture" in the freezing cold. I saw a TV segment on this one time but forget the details... How do hardwoods endure?

And neat use for olive oil, Tim. Must keep the hands in good shape too: good moisturizer. I wonder if car mechanics' hands would be helped by an olive oil pre-treat?

Slippery wrenches maybe aren't the best, however.

Either are chisels, unless you are talking slicks. Even a slick slick could be dangerous.

I use the latex gloves when turning wrenches.

Maybe the wood bmike was using had set in the sawyers yard for over 6 months with the exception of the one stick, which was sticky? At least it doesn't ooze pitch liberally and even after 160 years it can still be coaxed out. I hear dry kilns "set" the pitch, does it still run if put in the hot sun, I don't think it does? River cured logs are not pitchy, I am guessing the water dissolves the pitch? I have not tested river cured wood after 160 years, on the other hand a lot of wood came down the rivers, will that wood still ooze pitch?

Tim

I believe that sinker logs have the pitch and the bound moisture slowly forced out by the pressure and water of the lake / river. I seem to remember reading a technical article on it a ways back... If it is dissolving it, it is because the lake / river water is working its way deep into the timber.

Very well could have been in the yard for 6 months as logs. No unusual checking, and quite nice to work by hand. Like buttah, for the most part.

Don - enjoyable and informative as all your posts are.

But are you doubting there is any advantage to wintercut timber ?

How about winter cut and in the proper moon cycle, full maybe, waning or waxing?

Tim

I wouldn't say there is no advantage to winter cutting. I prefer to cut in winter but I don't know that it makes a huge difference. The big advantage I see is brightness. I'm not fighting bluestain in cold temps. I do wonder if there is more that our ancestors saw, or that you see?

Starch and sugar levels vary seasonally but it seems if there is a food source, something has evolved to take advantage of it. Enzyme and auxin and all kinds of chemicals change level in the sapwood throughout the year. I've wondered if ponding would help dissolve and lower the food levels stored in the cells, no idea. The heartwood, which is the more durable and less sticky part, does not matter at all as to when its cut as I see it. Notice the heartwood of the stump above isn't oozing. It is dead and beyond all caring of when it is harvested. It is also the wood we should be trying to get, heartwood is the good stuff. So if you're in the right timber I guess the "right time" is far less critical. A heartwood timber will not be particularly sappy where the sapwood has live resin producing epithelial cells ready to ooze in response to injury.

One way that plays out is that out of a reasonable pine I can get a 10x12 out of the butt log that is all heartwood and not sticky. The next bolt up can be a 8x8 that is mostly heart with sapwood corners. The next bolt is often a sapwood 6x6 with some really sticky waney edges. So depending on how a tree opened up can affect sappiness too.

Since bound water is the last to leave, only beginning to exit the cell wall at below fiber saturation point (<~25% MC). Ponding will keep the log's moisture level high so ponding shouldn't have any effect on lowering bound water levels. That isn't to say that some other factor related to the ponding isn't at work there during drying, like maybe ponding rinses out a water loving molecule of starch or sugar.

Resin is made of many compounds. The volatile compounds freeze, liquify, boil and vaporize at different temperatures. If a kiln runs the wood up to 160*F all the volatiles that will thaw, liquify and then vaporize at anything below that tempreature will be driven off. If the kiln holds that temperature for long enough, all of the volatiles for that set temperature are driven off. The pitch is "set" to that temperature. One reason pitch pockets still bleed at room temperature after kiln drying is that the large mass of pitch didn't "boil" for long enough to dry out the volatiles in the pocket, so the pocket is set for a lower temperature.

The moon cannot appreciably affect the moisture content or water columns would fail. The cells have to be saturated to live. Is there something else at work with moon cycles? I doubt it but I've been wrong plenty of times.

I've heard that in hot, dessicating weather, with the right equipment, they can hear water columns popping within the tree.

Don, the other thread moved on but "you" was directed at the reader in general not you personally, "we" might have been a better word choice .

I am now under the impression that the water, from the pond, "rinses out a water loving molecule of starch or sugar." That must be the factor for pond cured pine.

If the temp was raised above the 160 degree level once more, than the pitch would ooze again?

I read an article in The Small Farmers Journal which talked about the moon cycles and planting crops and cutting wood, it is almost a religion, to follow such methods, or is.

Tim