Why Do We Need Sapstain Control?

By Gary Schroeder (revised and reprinted from our Spring 1999 issue of Log Core newsletter)

Wood, and in this case the log, was a living substance; as soon as the tree is cut the biological breakdown of wood begins. The wood is protected for some time by first the bark and in the cold months of the year, temperature. As soon as the bark (shell) is removed, fungi can land on the unprotected wood and start its work. The steps of rot are mold and mildew, sapstain, white stringy rot, brown cubical rot and then just organic powder. The mold and mildew attack the surface to break the shell, then the sapstain goes into the wood deeper to start the transportation of water down into the wood to help decay. Next comes the white stringy rot with white filaments coming to the surface to seek out water and bring it deeper into the wood. Then the rotting fungi starts to basically unglue the individual wood cells to bring it back to powder.

If we can slow down the breakdown of the shell, then we can prolong the breakdown of the internal wood fibers. Through spraying on a diluted preservative, we can accomplish this task. Now not all woods deteriorate at the same rate, for the white oaks, cedar, redwood and many others have toxins within the wood cells to help retard the rotting process. However, the pines which are softwoods have a tendency to rot more quickly. Pine wood also has less density because the cells contain more air that permits quicker entry of the fungi. Enough of why, and on to what deterrents we can apply to the surface to retard the fungi.

We have several products out of a multitude of products on the market. The products we choose to carry are Sansin Timber-Tec, TM-5 First Treat, Sta-Brite P, and PQ-80. We carry these because they are more environmentally friendly than others. However, do not be fooled with the word “friendly”. Any material in stronger concentrates can still be unfriendly.

Sansin Timber-Tec is diluted 1:1 with water. Two options are available: M-30 provides the natural light color of fresh pine and C-20 provides a light honey color to the wood once dried. Its water repellency and UV protection helps during the construction phase

TM-5 First Treat can be diluted 1:1 with water, and in some rare occurrences can be diluted 2:1 if dry weather is expected or if applied to woods that do not sapstain easily. The ingredients in TM-5FT deter rot, sapstain, mildew and mold. However, because it is working within the wood and at times on the surface, it may not stop natural graying and mildew. If reapplied as the previous applications weathers off, it will repel mildew better.

Sta Brite P & PQ-80 are both super concentrated and can only be shipped from the manufacturer or picked up at our Grand Rapids, MN office. Stay Brite P mixes at the rate of 2.56 oz. per gallon or 12.8 oz. per 5-gallons of water, or as the contractor wants to mix it. This product is highly effective and has a bleaching agent in it that will lighten the logs. PQ-80 is similar to the Sta Brite P but contains Copper 8 quinolinolate that is safe for use on food boxes. This product leaves a brownish pigment to the wood. Note: These products are only sold to builders.

To Remember: Fungi need moisture to live. Because moisture is such an important factor to sapstain and rotting, we are mainly concerned about these during the time the wood is cut and to the point that it reaches 20% moisture content. Dry wood does not need protection of this type. Dry wood only requires a finish to keep it dry.

The other thing to remember concerning spraying on mildewcides and finishes is that it causes a film barrier to prevent other liquids from entering the wood. Because of this barrier, it is a requirement to break this barrier down at a later date by pressure washing to allow other products to enter the wood. Some people may wish to apply a borate product like PeneTreat before spraying on the sapstain control. This is permissible. There are different mixing application rates for PeneTreat and the sapstain controls. Because of these different mixing and application rates, it is best to spray them independently. This can be done in either of two methods. First, spray on before sapstain control or Second, pressure wash surface after the house is up and then apply the PeneTreat. This application is recommended so that the most amount of PeneTreat is absorbed into the logs prior to applying the finish.

Questions? Give us a call at 1-800-359-6614 or contact us here.