This invention provides a unique method of producing 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane ('BPTMC'). The disclosed method manufactures BPTMC from ketals and hemithioketals of 3,3,5-trimethylcyclohexanone ('TMC'). The reaction takes place in the presence of an acid catalyst, and optionally added co-catalysts. Additionally, applicants have disclosed a particularly useful method of manufacturing BPTMC from TMC and alcohol and/or thiol starting materials. These starting materials react to form the TMC ketal or thioketal materials. This method is particularly useful in that it allows recovery and recycling of the alcohol and/or thiol.