Nice share, I can assure that it works surprisingly well. The correct, or rather better, procedure however is:
1. Prepare MgSO4.7H20 (Epsom Salt) solution in Reverse Osmosis-ed (RO) or De-ionized (DI) water (Distilled water is a terribly expensive overkill).
2. Heat solution to saturate. Use 500g salt (more than 50% of Epsom salt is water anyway) per litre of water.
3. Drain all acid from the battery and flush it thoroughly with DI water then drain all the water.
4. Pour this solution in battery and gently shake for a while.
5. Put the battery to fully charge (may take up to 24 hours) on a proper charger, do not plug it in car or on UPS.
6. Do not cover the battery while charging, put it in well ventilated are, and DO NOT try to peek inside; those fumes can do the justice for good. Make sure it's not getting too hot while charging, reduce amps if so.
7. Once fully charged, it's time to fully discharge it. Use a simple constant load like a halogen bulb etc. Make sure it's not getting too hot while discharging, reduce load if so.
8. Repeat those charge-discharge cycles several times. Account discharging times, make a graph if that makes you happy. Once the graph levels out, it's good to go to the next step.
9. Drain out all the lassi from the battery, flush it thoroughly with DI water and drain all the water when it comes clean.
10. Fill it with fresh 1300 SG H2SO4 solution.
Only then it'd be useable for another year or so. If you leave Epsom slat in it, it'd die shortly.
Disclaimer:
There could be some mistake in my procedure/writing, I'm not a battery bloke, and it's half past 3 in the morning.
Just to put my two cents in:
I don't think many of us could even source right chemicals, or even water for that matter, in right purity- and the whole procedure is pretty lengthy and quite dangerous for an average joe.
I run a mineral water company; so naturally I have access not only to 99.999:% pure water, but also some of the world's purest MgSO4, and some man power to do it for good measure. Frankly, given all that I don't think it's something that even my younger brother would do, too much hassle.