Abstract: A process for forming a phenol formaldehyde resin, the process comprising the steps of: (i) reacting phenol with an excess of a formaldehyde material in the presence of an acid or base catalyst until water separates from the reactants as an immiscible layer; (ii) adding a mixture comprising an excess of polyhydric alcohol and an aromatic dicarboxylic or tricarboxylic acid, salt or anhydride thereof to the phenol and formaldehyde reaction mixture followed by addition of an alpha hydroxy acid; (iii) adding a non-aqueous solvent, wherein at least some of said water is removed either before addition of the mixture preparated in step (ii) or after addition of the alpha hydroxy acid; (iv) preparing a solution comprising a Lewis acid, a polyhydric alcohol, an alpha hydroxy acid, a non-aqueous solvent, an aromatic sulphonic acid and sulphuric or hydrochloric acid; (v) adding the solution formed in step (iv) to the mixture formed in step (ii) and allowing the mixture to cure.