Pressure Treated Timber
Greeny-blue speckles on surfaces of my timber product. Are they mould spots? 
Many of our products have been pressure treated so they last for many years. When pressure treating timber, a liquid preservative is forced into it in order to protect against deterioration due to rot or insect attack. In the treatment process finished timber is placed in a large container and filled with the preservative solution (normally greeny-blue in colour). As the pressure in the container   is   increased,   the preservative is forced into the timber. The excess preservative is drained from the container and recycled. As the timber dries some of the liquid evaporates from the timber surface, this can leave deposits of treatment salts on the timber surface, visible as greeny-blue speckles that can vary in severity. The speckling is very easily mistaken for mould. The pictures below show the difference between mould  and  speckling  left  by
the treatment. In all cases where the treatment salts are visible on the surface of the timber they can be left as over time they will fade. However, you can speed up the process by either pressure washing the timber and/or as we have done here, lightly sanded the effected area. reducing its appearance. Leaving what remains to fade as the timber naturally weathers.
Pressure treated timber with some speckling left by the treatment salts.  Pressure treated timber that mould has been allowed to grow. The difference between the treatments salts and mould is quite clear. A light rub down with sandpaper, even the most severe case of speckling left by the treatment can be removed.
Is mould detrimental to the product?
We take care to pack and store products so that mould isn’t able to grow. However on occasions it does happen, usually to product components in the middle of the pack, in areas where air  hasn’t been able to circulate. This provides ideal conditions for mould growth. Like the pressure treatment salts mould growth isn't detrimental to the product. The mould only grows on the surface of the timber and is easily wiped away with a wet cloth, brush or pressure washing. Once the product is assembled and out in the open air the mould will not return.