When some older plastics break down, they will begin to emit a unplesant odor. This scent has been described as similar to cheese or vomit. There's little to no information on how to remove this scent. This guide teaches you how, for a temporary amount of time.
The solution I have documented below only works temporarily due to how it neutralizes the smell. Eventually, your plastic will start emitting the smell again, and you will have to repeat the process. If you do not want to repeat this process, you may want to purchase a replacement. (Most) Newer plastic coatings have different compositions that prevent this problem from happening, but consider getting a metal/wooden replacement if you can. Due to the nature of the item, I could not do that.
I have also only tested this on thin plastic items such as rulers. I am unsure if it works for thicker items such as screwdrivers.
1. Get your supplies. You will need the following: Baking Soda, Something that can hold water, your plastic item.
2. Fill your container with water. I found warm water works better, but any temperature is okay.
3. Add Baking Soda. You should add enough that your water becomes cloudy, but not enough that it turns into a "slush." I eyeballed it, and added more as I saw fit. You'll probably use a lot of baking soda.
<-- my water looked like this after adding baking soda.
4. Add your items. Let soak. Generally, you will want your items to soak for a few hours. The worse it smells, the longer it needs to soak. I ended up leaving mine overnight to really kill off the smell.
You may see bubbles on your plastic. This is normal, and proof that it is working.
5. Take out your items. Dry them off via towel or air dry.
Your items may feel "gritty" or have white streaks/stains on them. This is just the baking soda, rinse it off with water.
Older plastic items were often coated with material that contained Cellulose Acetate Butyrate (CAB). CAB is usually odorless, waterproof, and resistant to oil and gasoline. These traits made it seem like a good choice for a durable, resillient coating.
However, all plastics deteriorate with time. It just happens that as CAB breaks down, it creates Butyric acid, which also is formed when bacteria break down fatty acid in butter (This means the butter has gone bad). This acid is oily, colorless, and emits the unplesant odor I described. This scent is much more noticeable if the item is stored in a small space for a long time, as it "traps" the odor and doesn't let it air out.
This smell is just a sign that the plastic is deteriorating.
Baking Soda/sodium bicarbonate is a base which can neutralize an acid. When interacting with Butyric acid, it creates the following chemical reaction:
C3H7COOH + NaHCO3 → C3H7COONa + H2O + CO2
C3H7COONa is sodium butyrate, which doesn't seem to have an odor despite websites claiming it does (If someone can explain to me why this is, I'd appreciate it and add it here. Thanks). The air bubbles you see in the reaction are the CO2 being released.
Of course, with time the CAB will continue breaking down and make more Butyric acid. Some people claim "sealing" the item works, but I haven't verified that.
I purchased a set of used ellipse-sets and various rulers used by drafters for a project to create some nice diagrams off a classmate (and since a professor required it.). When I purchased these, I took them home to realize they had quite an unplesant scent. I could not just buy a brand new set as this specific ellipse set (Pickett Ellipse Template Set 1224) has been discontinued, and listings online were going for hundreds more than they should. I am not spending hundreds of dollars on a single class, and I did not want to just throw out this set. I probably will store this and have to soak it every time I use it after I am done needing it. It's a nice set, all things considered, and works fine despite the smell, and I wouldn't want to sell/give this to someone else and give them a problem to deal with.
If anyone does know a new ellipse set that has the same measurements/dimensions of the Pickett Ellipse Template Set 1224, please email me.