Rutile question

Recently I fired my standard clear glaze.(Potash Feldsspar 19, Silica
19, Wollastonite 25,Podmore frit 2953 25,Microwhite China Clay 12.) (This
glaze started out as the 20,20,20,20,20 glaze on the Digital Fire web
site)

on a buff stoneware clay. Electric kiln fired to between cone 6 and 7.

The glaze was coloured with the addition of 5% red iron oxide and 5%
rutile. I used this combination after doing a cross blend. When it was
fired the rutile had formed patches of blue crystals where the glaze was
thick. These crystals also formed over a low fired stoneware white clay
as well but were not as obvious.

The questions are
Did the rutile react with the iron oxide?
Did the rutile react with the boron in the glaze?
Did the rutile react with something else in the glaze?
Could I get more crystals if I increased the rutile, iron or boron?
Do the crystals form on the firing cycle or on the cooling cycle?
If they form on the cooling cycle would a controlled cooling give more
crystals?

Cheers

John W