SP-11 is a formulation of non-toxic modified polymers with a high grade, high flash mineral solvent that contains no sulphur and has a very slow evaporation rate. Being water soluble, SP-11 penetrates the wood quickly and displaces the water. It coats the wood cells and capillary tubes to prevent them from shrinking as the moisture leaves during drying. This is similar to how Pentacryl works for stabilizing green wood. However, SP-11 is formulated specifically to compensate for the very high percentage of water in these waterlogged wooden artifacts.
When the treated wood is completely dry, a thin coat of SP-11 is left on the wood cell walls.
There have been many conservation methods to date including, but not limited to:
- Polyethylene Glycol, PEG
- Freeze Drying
- Alcohol Treatment
- Sucrose
All of these treatments have drawbacks and concerns of their own including the time it takes to impregnate the wood plus the treatments can involve a many step process and often include several types of treatments combined. The most commonly used method has been the use of PEG, Polyethylene Glycol.
However, there are some major drawbacks in using PEG to treat waterlogged or excavated wood:
- It is difficult to get it to penetrate and may require the use of heat elements.
- The penetration time is lengthy (can take several years or longer and often starts with a diluted solution).
- PEG adds significant weight to the wood and can darken it considerably.
- SP-11 is safe to use on wood that contains iron, such as nails, where PEG will eat the iron.
- It is hygroscopic making the wood sticky under humid conditions and requiring artifacts to be stored or displayed in climate controlled areas.