Parts Washers
Most shops will have a parts washer. They are nothing more than a tub that holds some kind of parts washing fluid. Sometimes they will have a pump to circulate the fluid, others will even heat up the fluid to make it more effective.
Types of Parts Washers
Solvent
A simple 20 gallon solvent parts washer will cost under $100 at Harbor Freight. If the tank evaporates too much and the submersible pump burns out, Harbor Freight has a $12 replacement.
Automotive shops use a solvent that requires Nitrile gloves (to prevent skin contact, prolonged contact can result in liver damage) and proper ventilation. Automotive shops also have large greasy parts, so they tend to hire services to swap out their solvent for roughly $80-$100 per month. There is no need for that frequency if for cleaning bicycle parts. If you buy solvent directly from a supplier it will cost roughly $60-$80 to fill up a 20 gallon parts washer.
- Solvent Pros: Cleans faster, lasts longer.
- Solvent Cons: Odor, hazardous material disposal, Nitrile glove expense.
Heated
Expect to pay over a $1000 for a basic heated tank, make sure the warranty is good for when the heating element burns out.
Simple Green can be used, while it doesn't work as well as solvent it smells good and you don't need gloves. To make it work even better it should be heated. However it does break down over time, and it can mold. Regardless of how bio-degradable it was pre-use, it is now mixed with non-biodegradable petroleum based products. Refer to shop recycling to learn how to dispose of hazardous materials.
Steam
Just use water.
Ultrasonic
No chemicals, just water and ultrasonic vibration, and parts came out brand new looking, even in hard to reach spots you can't scrub. Just soak, vibrate and dry off. You could even evaporate the water out the remaining gunk to reduce what you have to [properly] dispose of.
Examples
Salt Lake City Bicycle Collective
They used a solvent parts washer for 5 years and never cleaned their solvent, they just put more in as it slowly evaporates -- due to the dry climate, and people taking small quantities out of the tank, they go through ~10 gallons a year. Because of this the solvent is far from clear in color and the sludge just sits undisturbed on the bottom -- but it works just as well as new solvent.
Given the health concerns and smell of solvent, this was replaced with a modified a heated parts washer. The on/off switches for the heating element and the submersible pump were been replaced with timer switches -- so it is IMPOSSIBLE to leave on over night. This prevents having the heating element and pump burn out and having to replace the parts washing fluid. They purchase Oil Eater Cleaner Degreaser from Grainger and dilute it 1:3 with water.