This is from the Bethel Play Group from 1979. The ladies always made sure we had some in hand. Now I make it for my sons. It turns out well and keeps on the shelf for a REALLY long time in a freezer bag. When you first knead it, be careful, it is still quite hot.
Edited to add: I made two batches today. One used up some alum I had in the cupboard from last year. That one never really got to a good texture, and I had to add LOTS more flour. The second one used fresh alum, and it came together in no time and didn't need any extra flour. I made them using the microwave. I boiled the water in a large bowl first. Then added the salt. After stirring it in, I microwaved the water again for a minute just to make sure it was hot enough for adding in the food colouring (and subsequently, the alum and other stuff). It worked out perfectly. I tried adding in some lemon extract to give it a scent but it didn't seem to take.