Problem with VWP??

[Gilbo1]

I put a batch of bottle into a vessel of VWP, and unfortunately had to be called away for family, before i could finish the process. I have returned to the bottles some 3 weeks later and taken them all out and sterilised them all again in VWP. Now the water is draining from them, it seems that there is a grainy residue left on the inside of the bottles. Is it limescale, or does VWP separate over time if left in a solution allowed to go cold. Do you think they would be ok to use in this state, or would you ditch them??

[EliteEvil]

Rinse them with warm water and it will come off.

[Gilbo1]

Yeah i've tried that, and now ran them through the dishwasher with no avail. A tad annoying..

[EliteEvil]

Hmmmm don't know it worked for me when I had the same prob, but that was only after a few days.

All I could suggest then is a soak in soapy water, seems to help everything else.

[Dr.Evil]

I have the same problem with bleach-containing solutions. I have hard water, and adding bleach seems to cause the precipitation of limescale. Try an acid rinse to shift it, add some vinegar or citric acid to warm water and leave to soak. To prevent this next time, add some citric acid or vinegar to the water you use to make the VWP. Not too much, or you will turn all your bleachy goodness into chlorine gas. I add about 3 dessert-spoons of citric acid to a bath-full of water. (my alkalinity is 210 mg/l)

[Dr.Evil]

It seems unlikely to me that VWP would be sufficiently alkaline to cause permanent frosting of glass by the formation of silicates at ambient temperature. However, I think that alkalinity may indeed be the answer here, as the solubility of calcium carbonate (limescale) is inversely proportional to pH. It is also possible that the pH increase precipitates the calcium in the form of calcium hydroxide. In my experience, sodium hypochlorite (bleach) solutions do the same thing. They are also high in sodium hydroxide (caustic), both as a result of the manufacturing process and also to improve stability. I'd still see if an acid rinse shifts your residue Gilbo1. Kettle descaler may be a good choice.