If you listened to my Mailbag episode, you probably came away knowing that play-doh has a lot of salt, but maybe not certain what the other ingredients are there for.
In my exhaustive research, I found two versions of the Play-Doh recipe. The first is from the original patent, US 3,167,400, which lists the ingredients as follows:
Grain Flour (hard winter wheat flour, first clears)
Light hydrocrabon distillate such deodorized kerosene
Another patent I found seems to be for the same compound, but is an updated version filed a good forty years later. It’s US Patent 6,713,624, and it lists the ingredients as follows:
Potassium Dihydrogen Phosphate
Waxy Maize Starch C-Gel 04230
PEG 1500 Monostearate
So what are all these things?
Let’s start with the first formula. Something like 80% of all play dough is made up of flour and water, whether it’s the first formula or the second. That explains the first two ingredients. The formula does distinguish “winter wheat,” which is wheat that is planted in autumn and harvested in spring, as opposed to “spring wheat,” which is planted in spring. It also specifies “first clears,” which is a type of flour that is very high in protein. I’m not sure why these types of flour are called for in the original recipe, though it does seem that the original inventors of play-doh were trying to maximize the amount of protein available, as winter wheat also has more protein than spring. Why? Who knows? Well, the people at Hasbro know. But I don’t.
The water part in the recipe should be pretty straightforward, too--when you mix water with flour, you get dough!
The “common salt” referred to in the formula should also be pretty straightforward. The chemical name for common salt is “Sodium Chloride,” so you can probably see that there’s some more salt right there in the second formula as well.
Borax is also known as sodium borate, and it has lots and lots of uses. It was originally used in gold mining to help extract gold from ore, and it more recently has been used as a fire retardant, an ant killer, and an anti-fungal agent. In Play-doh, that’s most likely the purpose the borax is serving. Since Play-doh is basically just fancy bread dough, it wouldn’t take long on your toy shelf for it to start turning to mold. The borax keeps it fresher longer.
If you read lots of old books, you’ve probably heard of kerosene. Kerosene is often used as a fuel, to light lamps, fire, and the likes. In my humble opinion, the presence of kerosene in play-doh (while it won’t kill you) is probably a pretty good reason not to make a habit of eating lots of play-doh.
Though kerosene is mostly used as a fuel, it--like Borax--has a ton of other uses too. It can be used to clean bicycle chains, or to get candle wax off of a smooth surface. In play-doh, the kerosene (also called mineral oil) is probably helping the dough retain its smooth texture and preventing it from becoming too sticky.
I hope you can see by now that a lot of the ingredients in the second formula are the same as in the first. You’ve got your kerosene (now called mineral oil), your wheat flour, and your water, with sodium chloride (table salt) and calcium chloride (road salt) making up the salt. But what are the other ingredients? Well:
Aluminum Sulfate - Aluminum sulfate is actually an ingredient in baking powder, and it is used to make dough rise. It can also be used to kill slugs, so if you can somehow get it out of the play doh, it could come in handy…
Potassium Dihydrogen Phosphate - Though there are a couple possible uses for this chemical, it’s most likely in the play-doh as a preservative.
Sodium Benzoate - Here’s yet another preservative! Ever wonder why a jar full of flour and water seems to stay fresh for decades?
Waxy Maize Starch C*Gel - This is a patented type of corn starch, basically, which is there to thicken the dough and give it a more springy texture.
PEG 1500 Monostearate - Keep this away from heat and direct sunlight. And it’s also helping hold the whole dough mixture together.
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