underfires

Verb

underfire (third-person singular simple present underfires, present participle underfiring, simple past and past participle underfired)

1. (intransitive, transitive) To heat from below.
   • It was contended, that the only objection which could be raised against under-firing, was the danger of incrustation, or deposit upon the boiler bottom, of matter held in suspension by the water; but that this rarely, if ever, caused explosions; the utmost injury it occasioned, was causing the...1856 May, William Kemble Hall, “On the Causes of Explosions of Steam Boilers”, in John F[ries] Frazer, editor, Journal of the Franklin Institute of the State of Pennsylvania for the Promotion of the...
2. (transitive) To intentionally operate a boiler, furnace, oven, etc., at a low level.
   • The large supply of natural gas at Chicago permitted underfiring the batteries of the Chicago By-Product Coke Oven Plant with a mixture of producer gas and natural gas. […] The mixing of by-product coke oven gas with blast furnace gas to correct the varying thermal deficiencies of the latter when...1934, Wilbert J. Huff, “Gaseous Fuels during 1932 and 1933”, in A Survey of American Chemistry, volume VIII, New York, N.Y.: Chemical Catalog Company for National Research Council, →OCLC, page 339
3. (intransitive) To burn fuel at less than the desired level, thus not providing heat efficiently.
   • Often home owners select a [wood] stove that is too hot for the space to be heated. Many stove owners compensate by underfiring the stove, which causes poor performance, increased emissions and potential chimney fires by creosote buildup.1999 June, “Homes & the Canadian Experience”, in Alexandra R. McKirdy, editor, The Canadian Renewable Energy Guide, 2nd edition, Burnstown, Ont.: General Store Publishing House [for the] Solar Energy...
4. (transitive) To fire at a low (or excessively low) temperature.
   • You no longer need to underfire your products or guess at their high temperature behavior simply because of lag in furnace technology.1973, Ceramic Industry, volume 101, numbers 2–6, page 68