Askomiele, There were two early types of auto dry: Temperature and Time/Temperature. Westinghouse had a dryer with the strictly thermostatic auto dry control in the early 50s that had a dial marked 1-9 or 1-10(?). That was how you selected the level of dryness. Delicate fabrics or clothes that were damp dried for ironing were dried at the lower numbers, heavier fabrics, the higher ones. Basically when the dryer reached that temperture, it shut off. That is how the Blackstone control worked. I guess that is why they could use such a small dial, because you were not setting a timer. Westinghouse came out with a dryer in the mid 50s that had a timer dial with a large portion of the dial for the timed cycle, but also had a portion of the dial labeled DRY. When you used that cycle, the dryer ran until the exhaust temperature reached somewhere around 220 or 230 degrees F and then it just shut down; no cool down, it just stopped. With these systems, the heat did not cycle on and off, the dryer just kept heating until it reached a temperature that correlated with a level of dryness that the manufacturer had worked out. In the early Westinghouse and the early Blackstone, the user had some control over the degree of dryness so lighter weight fabrics and Nylon (the synthetic fiber at that time) could be dried in the dryer. The later Westinghouse DRY cycle was only for cottons. Heat sensitive fabrics were dried on the timed cycle and low heat could be selected.
Later came the gentler Time/Temperature Auto Dry where the temperature was held at lower operating limits and cycled on and off to maintain the temperature. In the automatic cycle, when the heat cycled off, the timer motor ran and when the heat cycled on, the timer motor stopped. As the clothes became drier, there were longer periods when the heat was off and the timer motor ran more which eventually put the dial closer to the OFF position. Three to five minutes before the dryer shut off, the control dial advanced into a zone where there was no longer any connection to the heater circuit so the clothes tumbled in unheated air and just the residual heat of the dryer. Since the heat level in these dryers was lower to begin with, the clothes were not uncomfortably hot to handle when the dryer shut off.
