First thing you need to know is that Bakelite and Catalin are two different plastics, but are both commonly referred to as Bakelite. All of the "Bakelite" jewelry that you see is actually Catalin. Bakelite was generally only used for electrical appliances, handles on pots and coffee pots, etc. because it will not melt. Bakelite/Catalin exposed to open flames will only char. Knowing how to test for Bakelite and Catalin can also help you date other items that have Bakelite or Catalin elements, i.e. handles. Bakelite was invented in 1907 and Catalin came around in 1928. The use of Bakelite and Catalin for everyday items pretty much died out after WWII. Therefore most items containing Bakelite or Catalin elements are from around 1907-1945.
Bakelite is a thermoset plastic made out of formaldehyde, phenol and a filler to make the product stronger and cheaper; usually wood, rags, cotton, and sometimes asbestos. Therefore it should not be reworked, it could be very harmful to your health. Also because it has filler in it, once the first layer of Bakelite is destroyed it is impossible to restore to its original luster. True Bakelite was only made in two varying colors: brown and black. It could only be made in these two colors because of the extreme heat it endured while being cured.
Catalin is also a thermoset plastic made of formaldehyde and phenol with no fillers. Therefore it can be restored and reworked (using the right saftey precautions of course). Catalin is usually very colorful. Over time Catalin develops a patina, there is NO white Catalin (unless it has been restored, reworked, or has never seen sunlight). Sunlight causes the Catalin to yellow or "petina". All of the original white Catalin has yellowed over time, and clear to "apple juice", blue to green or teal, purple to brown or tan, while green, orange and red stay about the same. White marbling in marbled pieces will be yellowed. Catalin also shrinks over time, that is why most of the radios have cracks, warping, and the fiberboard on the back no longer fits.
The hot water test is by far the most accurate, though you must have a good nose and know what formaldehyde smells like. You can just hold the piece under hot running water or you can heat some water in the microwave and dip the piece in the water. Submerge the piece for 15-30 seconds. Immediately smell the piece. If it is Bakelite or Catalin it will smell like formaldehyde. Celluloid (another vintage plastic) will smell like camphor or Vicks Vaporub. If it smells like rotten or burnt milk it is French Bakelite/Galalith. Once you know the smell of Bakelite/Catalin you will never forget it. This test will work on all pieces no matter the color or if it has been reworked or restored.