Crystallised sod. metaborate

[ColinRH]

I made my first batch of PMK Pyro in September last year. I am about 3/4 way through it but noticed over the weekend that Part B has thrown a sort of crytalline deposit. I don't know how long the solutions should last so disposed of it and made some more with 500ml of filtered tapwater and 150g of sod. metaborate.
When I opened the plastic pot it had been sold in, the crystals had clumped together to form quite large pieces. I thought nothing of it and with the water at about 55 degrees mixed the sloution and put it in my storage cupboard which has a pretty consistent temp of about 65 - 75 degrees.
Today I went to use it and at the bottom of the plastic container were large crystals, like sugar, with some stuck together in larger pieces like ice crystals!!
Where have I gone wrong?

 

[anikin]

Part B is a saturated solution of sodium metaborate. Cooling it down will cause crystallization. Just heat it up, stir and it should dissolve back.

 

[anikin]

Uhm. Tap water? The directions specifically recommend distilled water because you are making saturated solution. See:

http://www.jackspcs.com/pmk.htm

 

[ColinRH]

Uhm. Tap water? The directions specifically recommend distilled water because you are making saturated solution. See:

http://www.jackspcs.com/pmk.htm

I know the difference beteween distilled and de-ionised water, but do you think the link actually MEANS to use distilled. So often it seems that de-ionised is fine.
As for the solution being a saturated solution; again I understand the basic meaning of such a solution but should it crystallise out as easily as it appears to have done? It was hardly in a cold store when the ambient was about 65-75.

 

[anikin]

I know the difference beteween distilled and de-ionised water, but do you think the link actually MEANS to use distilled. So often it seems that de-ionised is fine.
As for the solution being a saturated solution; again I understand the basic meaning of such a solution but should it crystallise out as easily as it appears to have done? It was hardly in a cold store when the ambient was about 65-75.

Well, I'm not a chemist, but when you are making a saturated solution, lowering its temperature even a little bit usually causes crystallization, especially if you have impurities in the water. That's how some of those crystal growing kits work . I suspect that in this case they actually mean to use distilled water. De-ionized should be ok, but I would avoid using filtered water which always contains some ions.

 

[paul ron]

If you are getting crystals droping out, you are super saturating the solution.

 

[brucemuir]

I have one of the PF liquid PMK kits I've been pulling from since about 2005.

I store in my basement darkroom where it can get down to 60-64f in the winter and it even got down to the low 50's during the power outages this winter.


I've never seen any crystals in my part b.

 

[ColinRH]

Thanks for all your comments - I shall note all the observations and in the first instance use distilled water; then if necessary try cooler storage and finally reduce the ratio, although most recipes I have seen state 300g S.M to 1lt water. Thanks again