THF (Tetrahydrofuran) is a solvent that is commonly used to reduce the viscosity of liquid PVC or lacquer sealant. These products leave the factory with the correct viscosity, but as they are made from volatile solvents, their viscosity increases over time. To reduce it, a small amount of THF is added to the polyethylene bottle containing the sealant.
It can also be used as a cleaner for PVC fittings (pipes, pipping, etc.), prior to the application of the specific PVC glue.
Colourless THF solvent, 1 litre bottle