We built several prototype dryers using various size heating elements and different flow rate fans and tested these units by placing thermometers throughout the interior of the dryer.  We were very disturbed to find that the temperature inside was very stratified, hot at the top and cool at the bottom.  We tested other units and found the same was true throughout the spectrum of available dryers.  The most obvious solution to this problem would be to increase the power of the fan at the top, but too high a flow rate causes turbulence inside the dryer and the film starts to blow around . After reevaluating the problem we installed a small exhaust fan at the bottom of the dryer and the stratification problem was solved.

Another problem not addressed by competitive dryers is exhausting the moisture being shed by the drying film.  If you look at the bottom of most dryers you will find inadequate venting.  Essentially most dryers are steam cabinets with hot dry air at the top and cold moist air at the bottom.  By using a two stage system our dryer moves the moisture out and away from the film faster,  and cooler temperatures at the top of the dryer minimize the possibility of reticulation.

The dryer has two controls.  A 60 minute timer with a hold feature  turns the dryer on and off.  A three position toggle switch has high and low heat positions and allows the heating elements to be turned off altogether.  High heat position is ideal for drying prints or large batches of film.  Low heat can be used for small batches of film .  Fan only position is provided for thin base 220 roll films which curl with forced heat drying, and this position can also be used as an energy saving feature.  High heat element in this dryer is 1000 watts, low heat is 500 watts.