white crystalline on transformer

[deetz]

I opened up a 45kva dry transformer that was not in use for a few months to put it back in use. It's hanging from the ceiling of our facility. on each mount where the coils are, and the rubber pads are, there is a white crystalline foamy looking substance that pretty much disintegrates when you touch it. I'll clean it all off, but am worried something is wrong. It is grounded to building steel and the Buss that feeds it. We have quite a few other transformers hanging, and haven't seen this on any other ones. Any suggestion as to what it is and what I can do to prevent maybe it building up again and not have it build so much that it shorts the unit?