Two resole-type phenol formaldehyde resins were synthesised with a formaldehyde to phenol (FP) molar ratio of 1.2 and 1.8 and their structure on curing examined by C-13 CP-MAS solid state NMR. The FP = 1.8 material was considerably more complex than the FP = 1.2 material. This has been interpreted as due to the formation and subsequent cleaving of ethers in the FP = 1.8 system. The structural changes in each resole after heating were observed by C-13 CP-MAS NMR up to 500 degreesC, and their surface areas after carbonisation at 1000 degreesC were measured using N-2 and CO2 gas adsorption. The FP = 1.2 material was found to possess narrower micropores than the FP = 1.8 material. These results are significant for those industries where the high-temperature behaviour of phenol formaldehyde materials is important. (C) 2001 Elsevier Science Ltd. All rights reserved.