Kalk shelf life?

[Son Of Skyline]

I just tried mixing a bucket of kalk water with 1 year old kalk (i had it for about 1 year...got it from Shao. Not sure how long he had it). After 48 hours the water is still cloudy white. The last time I used this stuff was about 6 months ago and the solution would clear in less than 12 hours. How long does kalk powder usually last before it goes bad? It's been kept in a closed ARM media container unused for the past 6 months. Thanks.