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Every three months or so I draw any liquid sealant out of my tyres and pour it back into my open Stans bottle. Giving the bottle a good old shake I add the correct amount back into my tyres. Am I diluting fresh (good) sealant with old (ineffective) stuff? Or, provided it remains in liquid form, is the stuff from my tyres as good as the stuff in the bottle? And if you keep a bottle on the shelf, what's its shelf life?
Dunno maybe best asking them direct.
Why do you take it out?
I have it in my front tyre and it has been in there for 3 years. When it goes down I pump it up and it is fine.
I have never added or removed any liquid.
Why are you doing this?
I've got the Milkit system and the syringe can draw the sealant out so you can measure how much is in the tyre. I figure it's best to replenish with sealant mixed into the bottle rather than top up leaving what's in the tyre. No science applied - just a gut feel.
I think you’re probably slowly decreasing the effectiveness of your stock solution. I get that being able to easily remove sealant is a huge part of the point of Milkit, but I saw that in the context of serial tyre swapping and possibly racing.
My far less elegant maintenance routine (which I suspect is fairly normal) is to shake the wheel by my head whenever I remember and it’s off the bike, and add a bit more if I don’t hear sloshing.
Bear in mind that once the wheel is set up, the liquid Stans is only protecting against damage rather than ‘keeping the wheel airtight’ - there’s a big distinction.
The latex itself is unlikely to become less effective but the soup of stuff to keep it viable and liquid is prone to evaporation (ammonia, antifreeze etc) so you may actually be brewing a ‘super Stans’ that will plug bigger holes (possibly slower) as the viscosity and volatility will be changing but you’re almost certainly altering what’s in the bottle.
Possibly continue with your fluid drawing if you like the routine, but once drawn, note the quantity and return directly to the tyre and then add additional fresh to your preferred quantity?
Stans forms bogies over time. I recently took a tyre off a rim that had been lying around with Stans in it for a year. There was a lot of solidified latex in the bottom and a very watery liquid. So in cool weather your mixture might get weaker, in warm eather maybe stronger.