Does Mineral Spirts go bad?

Here's an answer from AI:

No, mineral spirits do not go bad or expire over time. They can be stored and reused indefinitely as long as they are kept in a sealed container. Here are the key points about mineral spirits not going bad:

- Mineral spirits themselves do not degrade or lose their effectiveness over time.[1][3][5] They have an indefinite shelf life when properly stored in a sealed container.

- Any cloudiness, residue, or "cottage cheese" appearance in used mineral spirits is simply paint, stain, or other materials that have mixed in and settled out.[4] The mineral spirits themselves are still usable.

- To reuse cloudy mineral spirits, simply allow the solids to fully settle to the bottom, then carefully pour off or filter out the clear mineral spirits on top.[1][2] The filtered mineral spirits can be reused for thinning paints, cleaning brushes, etc.

- Mineral spirits may evaporate over time if the container is left open and unsealed.[5] But in a properly sealed container, the mineral spirits themselves will not degrade or expire.

So in summary, while mineral spirits can become contaminated with solids from use, the mineral spirits liquid itself does not go bad or lose potency, even after many years of storage in a sealed container.[1][3][5] Any cloudiness can be removed by settling and filtering, allowing the mineral spirits to be reused repeatedly.

Citations:
[1] https://www.wikihow.com/Dispose-of-Mineral-Spirits
[2] https://ergenvironmental.com/solved-how-to-dispose-of-mineral-spirits-the-right-way/
[3] https://www.whiteblaze.net/forum/showthread.php/20782-mineral-spirits-expiration
[4] https://www.diychatroom.com/threads/mineral-spirits.175608/
[5] https://www.woodmagazine.com/wood-supplies/finishes-finishing/will-my-finishing-solvents-go-bad-over-time

Thanks I looked it up before I asked the question.  I figured I would get some real world answers.

I didn't know the answer and was surprised that not only doesn't it go bad, but it apparently doesn't lose effectiveness after being contaminated with with solids which can be settled or strained out. I wonder if there can be other things in paint and stain that don't remain solid and go into solution with the spirits.

@Admin. I had the same concern.  I switched to paint thiner to see if it does better then the mineral sprits.  I will know in a few days, I only haven more coat on these shelfs before I move on to the cabinets again.

I've not been happy with MS subst. It had all the disadvantages of the real, and more. Strange cleanup being one. If I recall, the stuff has a fine suspension of water in the original makeup. Water freezes. Also, "thinner" defines a function, not makeup. Read the boring stuff in the alphabet soup data sheets, as well as independent experts; Flexner is your friend.

When you have a quickie finish job, foam brushes may work. But call me a prissy for preferring expensive real brushes, which demands better cleanup agents.

I am using Kleen Strip mineral spirts substitute.

Oh, so it's a mineral spirits substitute. I interpreted that as it was a generic mineral spirits instead of the brand name Kleen Strip. If that is the case, then the AI response may not be accurate as chemically it is different from mineral spirits.

So chemically, what is the MS substitute? Water? Jack Daniels? 

To reduce odor and VOCs, the formula likely includes oxygenated solvents or additives that are more prone to oxidation and degradation over time compared to pure hydrocarbon solvents.

Curious, did the brushes seem "less clean" over time indicating there may be residue of whatever you were using them for?

@Admin  No they seemed fine.  I could take them out of the cardboard and they felt fine.  I would brush them against my hand and look for loose bristles, and they flowed fine.  I had to run up to MO for a HS Graduation, so I left them or four days.  When I went to use it, it was stuck to the cardboard, and as hard as a hammer.  

The paint thinner seems to be working fine.  I won't use th brush for the next few days so I will see.

Years ago I tried to reduce the amount of paint thinner I disposed of by letting it sit until the paint residue settled out. Eventually the liquid at the top looked plenty clear enough to use for thinning paint and cleaning brushes. After that all I disposed of was the paint sludge and I never had problems with the recycled thinner.

One other point I'll mention is the difference between traditional paint thinner and traditional mineral spirits: to be sold as mineral spirits there's a higher level of purity required. Otherwise they're chemically the same.

I have reused mineral spirits for years.  Someone told me about letting it settle & ever since I have a couple of containers in various stages.  Settling, settled out & useful for first wash or cleaning & degreasing.  Once got about 12 gallons from a painter doing job with an orange catalyzed finish.  Let it sit in the containers I got it in for a few months & everything cured & settled.  I used that for first wash general cleaning for years.