Coolant ickification, and disposal
I have a small home brew flood coolant system for my mini-mill. The mill sits in a shallow tub that drains into a bucket. I have a small fish tank pump in the bucket pumping the coolant up through a small adjustable manifold that squirts it onto the tool. Works great for my basic needs.
I keep 1 gallon of coolant in the reservoir. A 1:4 mixture of Kool-Mist and water. I've noticed that the coolant tends to get "funkified" when under heavy use. If I were to just let it sit there for, say a month or two, it'll stay fairly clear. But if I have a real busy weekend and run the mill for maybe 3-4 hours, the whole mixture clouds up and gets noticably more viscous. When fresh, it's not a whole lot different than blue water. But upon funkification, it really starts to get gooey and takes on a grayish tinge. It still works perfectly fine, but it's gross. What exactly causes this? Is it colloidal metal gunk getting mixed in, or what?
Second - what's the best way to dispose of this? By the time I need to change it up, the reservoir typically has about 3/4 gallon of fluid left with plenty of chips mixed in. I'm hesitant to pour it down the bathtub drain, but I dunno where else to put it. Do gas stations take soda bottles filled with random liquids?
If it is turning grey it is probably metal in suspension. Put a particulate filter inline with the pump - that way your pump will last longer and you won't be pumping metal back onto your work. Isn't Kool Mist designed for misting and therefore has little lubricity? You may want to rethink your coolant choice.
As far as disposal, call Safety Clean. If you machine any lead bearing metals you could be in for a surprise ($$$$) if you get caught dumping it. Also, call Kool-mist and ask them how to dispose.