Brian Fistler on mon 3 jul 06
On Mon, 2006-07-03 at 08:41 -0500, Bob Cope wrote:
> Substituting TiO2 for Rutile=ADshivering?
>=20
> Hello, I=A2m using MC6G=A2s Variegated Slate Blue,
> and in an attempt to solve some minor pinholing,
> I substituted 6% TiO2 for the 6% rutile.
> The color was great, but the resulting fired
> cylinders had shivering on the rims. Before the
> substitution I had had pinholing but there
> was never any shivering.
> Could this single substitution cause shivering?
> All other variables were controlled to the
> extent possible. Thanks for any help!
>=20
> Bob Cope
> Madisonville, TX =20
Bob,
The *calculated* thermal expansion for the recipie comes out almost
exactly the same if it's TiO2 or rutile. (Actually the TiO2 shows ever
so slightly higher expansion.)
Did you fire both batches to the same temperature? How about the bisque
firing? Was one of the two glazes possibly put on more thickly than the
other.
If you have any of the "origianl" rutile pieces still around, you might
try doing a thermal shock, freezer to hot water (use caution) to see if
it will shiver. It could be that on your clay body the Rutile-based
glaze was very close to shivering, but do to different cooling rates or
some very small variation on the two batches the TiO2 batch shivered
where the rutile batch did not.
Did it at least solve the pinholing problem? :)
Brian
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