This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
At this stage a few negatives may be helpful. Here they are. Don't be in a hurry. Don't think you can force a daffodil against its will. Don't burn so many tons of coke or coal without occasion, for, paradoxical as it may seem, undue heat too early applied exercises a retarding influence on the crop, and a much later introduced batch of the same variety, more rationally treated, will precede the first in its flowering. Fourteen days coldhouse treatment for all early kinds is essential, and the time may be extended advantageously. Watch the crop and its progress under these conditions and apply heat gradually with caution and intelligence. Until growth is well in sight and the flower scape is clear of the orifice of the bulb's neck a temperature of 45° F. will suffice: but when these critical stages are successfully passed a considerable rise in temperature may be given.
Avoid the close proximity of hot-water pipes; the arid conditions experienced are opposed to growth. Avoid root dryness at all costs; Daffodils revel in moisture, and in the forcing house it can hardly be overdone. Atmospheric moisture in conjunction with root-applied moisture conduces to free growth and long, characteristic stems - the latter a valued asset in the forced Daffodil.