Abstract: A process is disclosed for controlling the furnace temperature in a manufacture of phenolic resin-treated honeycomb structures from paper webs. The phenolic resin-treated honeycomb structures from the paper webs are, preferably, glued together and shaped to a body. Such body is immersed into a solution of a phenolic resin mixture and subsequently dried and cured in an indirectly heated furnace. The immersion and drying/curing steps may be repeated several times and take place at a temperature in the range of 70.degree. C. to 110.degree. C., except for the last drying/curing step, which takes place at a temperature in the range of 145.degree. C. to 155.degree. C. For controlling the temperature, the substances contained in an air mixture exiting from the furnace are preferably condensed and subjected to fractionated distillation with the temperature of the furnace preferably being adjusted, based upon the quantities of organic and/or inorganic compounds obtained.