This is merely a short but necessary clarification to the previous references to diluents. “Thinners”, as a term, covers both what is used to clean brushes, and what is used to dilute paint for artistic purposes. Whilst standard decorators’ quality White Spirit is satisfactory for brush-washing at the end of the day (as long as it is rinsed out of the brushes with water immediately afterwards), it is not good enough to be used in the actual painting process. For this artists’ quality Turpentine is probably the best. Although White Spirit is produced to artists’ quality and sold as such, it lacks any trace of the gummy residue which all natural Turpentines possess, and which acts as an assisting binding agent when paint thinned with Turpentine is dry. By contrast, the oil of paint thinned with White Spirit is more molecularly disrupted, and dries to a slightly less stable film.
To risk repetition, decorators’ quality Turpentine, as sold in DIY stores, is NOT suitable as a diluent for artistic purposes.