Another of my many hobbies is making bath and body products out of cheap stuff around my house. I went on a recent scouring of the internet, and found a lot of recipes relating to oatmeal (because I found a container of just expired oatmeal) and baking soda (because I found a huge honking Costco sized box of it).
One suggestion was to grind the oatmeal into a fine powder, then mix equal parts of oatmeal powder and baking soda with a little bit of water to make a paste, then smear this on your face as a masque.
After coming back from my daily walk on a particularly cold day, I decided it was spa day. I poured some bath salt into the tub, mixed up my oatmeal and baking soda, and sat in blissful luxury until I was thoroughly pruney. The face masque was fantastic, and left my skin feeling glorious.
But wait! There's more! We haven't gotten to the mishaps yet.
The next day, I'm washing my face, and oh! there's the rest of the oatmeal/baking soda mix. Thinking of making my own replacement for St. Ives scrub, I added a little bit of the mixture to my soap and started scrubbing away.
Suddenly I smelt a smell. A cloying, nasty smell I was very familiar with from both chem lab and cleaning: ammonia.
I frantically checked the back of my soap bottle to check the ingredients and sure enough, right after "water" on the ingredients list was "ammonium laurel sulfate".
Here's a little chemistry lesson for y'all. Soaps, and their cousins detergents, are a salt composed of a fatty acid with a proton removed and some anion. Baking soda (sodium bicarbonate) is also a salt. Sometimes, when salts come into contact with each other, they will switch cations and anions, a reaction known as ion exchange. That would leave sodium laurel sulfate and ammonium bicarbonate.
Now bicarbonates are notoriously unstable, and will often decompose into carbon dioxide. Sure enough, when I checked Wikipedia, ammonium bicarbonate decomposes at 36 C (about 97 F) into carbon dioxide, water, and ammonia.
For those of you who don't know anything about science and who skipped the last two paragraphs, what this boils down to is I HAD AMMONIA ON MY FACE. (For those of you who REALLY don't know anything about science, that's hella bad.) After frantically rinsing my face for about 10 minutes and doing the "ewwgetitoffgetitoffgetitoff" dance, I was fine, and none the worse for wear.
However, I would like to share my little hard-learned bit of wisdom with the rest of the world, so that nobody else has to suffer the same fate.
That's not to say that it's a bad idea all the time. Baking soda is a chemical pH neutralizer, as well as an excellent exfoliant. Just make sure that your soap is made with a sodium or potassium detergent. (Most are made with Sodium Laurel Sulfate or Sodium Laureth Sulfate. Since sodium can't very well do an ion exchange with itself, it's perfectly safe to put baking soda in with these substances.)
That said, here are a few of my favorite cheap-ass home spa recipes.
OATMEAL HONEY FACE SCRUB
1 c oats
1/4 c almonds or walnuts
1/4 c honey
Grind the oats and nuts together in a coffee blender. Microwave the honey so it is nice and runny, then add to the oat/nut mix and blend together. You may also need to add a little bit of water. Spread over a moist face, gently rubbing in small circles for several minutes. Rinse off with warm water.
3/4 c Epsom salt (magnesium sulfate)
1/4 c Rock salt (sodium chloride)
3-4 drops of your favorite essential oil or extract
Pour it all in the bathtub, let it dissolve, and sit there soaking for about half an hour. This is great for sore muscles or mild sprains or pulls.
1 c sugar (can be granulated or brown)
1/3 c oil (lots of people use olive oil: that's too expensive for me, so I use canola)
handful of crushed herbs or tea
3-4 drops of essential oil or extract
Just scoop some of this stuff up and scrub it anywhere you need exfoliated. Safe for use pretty much anywhere except your nether regions. If you use it on your face, be careful there isn't too much moisture, because otherwise the sugar will dissolve and run into your eyes.
This allows for an amazing amount of customization. I have made lavender, spearmint, peppermint, rosemary and mint, brown sugar and spice, chamomile, lemon, ginger, and vanilla scrubs before. Dink around with it and see what you come up with.
P.S. This is my favorite way to get rid of that box of tea in the cupboard that's been sitting there for years that nobody drinks.