when adding oil to water stir water vigorously adding oil VERY slowly.

If it does not walk like a duck its probably not.

Soluble oils are not really soluble, they just have an added surfactant. This helps the process of the oil breaking into small droplets and reduces water surface tension to keep the small droplets in suspension and so form an emulsion. It is possible the surfactant had been damaged by frost but I don't know. All the soluble oils I have used I just put the correct volume into a hand sprayer then added the water (rain water from a water butt to avoid any hard water salts) followed by a quick shake, with the top on, to mix the two.

I would just assume it is no good and replace it with something you know is really a cutting oil that has not been frost damaged, it goes a long way when diluted down with water so the cost is not too bad.

Martin C

Nothing to be lost by adding a squeeze of washing up liquid

You only want a couple of drips of washing up liquid to a bucket full of water, it’s a p*** in the ocean amount, the couple of gallons of water will do more harm to your machine.

Electrolytic corrosion requires an electrolyte. Water with salt in it can act as an electrolyte, salt free water is a very poor electrolyte and salt absorbs atmospheric moisture as well. Not a good idea to have even a very small amount of salt water on ferrous metals. If the majority of water evaporates the salt is left behind. I have seen problems with steel and stainless steel corroding because a hot water bath used to clean off dye penetrant products and flash dry the part was filled with tap water instead of demineralised water.

Martin C

+1 No need for Beardy Mike to take a risk though because the risk is easily tested.

Take two shiny nails. Half submerge one in a jar of clean water, and the other in a jar of suspicious suds made with a dash of detergent. Compare how quickly the nails go rusty. If the suds are good, the nail should rust much more slowly than the one in plain water.

Expect quick rusting if the detergent contains an Anionic Surfactant – most Washing-up liquids do. I like John Haines suggestion though – unlikely that Car Shampoo has anything in it that encourages rust.

Might be easier just to buy new and protect from frost. However, whether a cheapskate remedy works or not is always entertaining. There should a Model Engineering Award for the most audacious use of an unknown potion in the workshop. Special category for traditional methods known to be dangerous because these are widely believed to work better than any modern preparation. Volunteers needed: Red Lead makes an excellent cutting paste! Double points scored if the operator chain-smokes Capstan Full Strength whilst machining.

I believe Science doesn't understand how surfactants work – anyone know? For example, seems unlikely that a smear of WD40 would make any difference when cutting Aluminium, and yet it does – a big difference. Thought to be something to do with the electronic bonding between atoms that occurs at surfaces, causing hardening at the boundary. How much depends on the materials in contact. HSS biting deep into Aluminium has no effect on surface hardening, but a drop of surfactant weakens it considerably. Then HSS cuts better.

Whatever causes boundary hardening gets stronger the more a surface is polished. That suggests to me it's related to the powerful force that sticks wrung Gauge Blocks together, another scientific mystery.

Dave

as others have said its unlikely to be what it says on the tin. could be previous owner used it as neat cutting oil, got decanted into any available container to get it home