Geoff Walker on tue 25 apr 00
G'day Brad,
I think one of the reasons you are getting pink "fleeting spots" in your
rutile glazes is because there is enough Chrome as an impurity in most
rutiles to blush the main constituent, titanium. Very little chrome is
needed as it is a very strong colourant, and also very volatile.
Some weeks ago I posted on the subject of chrome blushing titanium in
glazes, but no-one picked up this potential thread, to my amazement, I
have to say. We use this phenomenon in two or our glaze combinations. In
one, the chrome in a splashed glaze-on-glaze blushes the base (high
titanium) semi-matte glaze apricot/pink, whilst in the other (a rich
buttersotch colour at ^ 10 reduction), the colour is due to chrome
volatilizing from surrounding dark green glazes and attacking the very
high titanium content of the butterscotch. Without substantial
quantities of green glazed ware in the kiln, the butterscotch glaze is
more like fresh butter in colour ... a little anaemic, to say the least.
Despite there being countless references to chrome/tin blushing, I have
yet to read anywhere of chrome/titanium blushing. Mind you, I have often
seen bathroom tiles (in '70's bathrooms when orange was a popular
decorator colour!) in which I am sure this phenomenon has been utilised.
Anyone else experienced this?
Geoff.
Oh! ... and I have found it only necessary to use 50% more "Zircopax"
than Tin Oxide when substituting. The base glaze could dictate this
quantity, however. The silica content of zircopax will also affect the
ratios and expansion. One tin glaze I used years ago used to craze, but
making the above substitution corrected that defect. G.
Brad Sondahl wrote:
> ----------------------------Original
> message----------------------------
> Changing to zircopax should eliminate the pink problem. I only get
> pinks now in high rutile glazes (in fleeting spots). Most texts say
> to
> double the amount of Zircopax to get similar whitening. I use up to
> 15
> % to get a really white glaze. Zircopax doesn't melt in the mix, so
> doesn't interact much with the glaze chemistry.
Darby Ortolano on fri 28 apr 00
Hi Geoff,
I too have noticed that chrome caused a pink blush in my 04 firings. I was
experimentiong with glazes over majolica, and one of them was GB 80%
Titanium Dioxide 20% (Peeling Paint recipe). To my surprise (and delight
being a fond lover of pink) the result was a lovely luminous glow. I didn't
realize at first that this was caused by nearby stains with chrome in them,
but when I began to suspect that it was , I brushed the Peeling Paint over
chrome lines on the majolica and got the blush (much like what copper will
do in high fire reduction). If too much chrome the pink is quite ugly. Am
considering developing a glaze to take advantage of the glow.
So, you are not alone in your experience with chrome blushing titanium!
Darby
> Some weeks ago I posted on the subject of chrome blushing titanium in
> glazes, but no-one picked up this potential thread, to my amazement, I
> have to say. We use this phenomenon in two or our glaze combinations. In
> one, the chrome in a splashed glaze-on-glaze blushes the base (high
> titanium) semi-matte glaze apricot/pink, whilst in the other (a rich
> buttersotch colour at ^ 10 reduction), the colour is due to chrome
> volatilizing from surrounding dark green glazes and attacking the very
> high titanium content of the butterscotch. Without substantial
> quantities of green glazed ware in the kiln, the butterscotch glaze is
> more like fresh butter in colour ... a little anaemic, to say the least.
>
> Despite there being countless references to chrome/tin blushing, I have
> yet to read anywhere of chrome/titanium blushing. Mind you, I have often
> seen bathroom tiles (in '70's bathrooms when orange was a popular
> decorator colour!) in which I am sure this phenomenon has been utilised.
>
> Anyone else experienced this?
>
> Geoff.
>
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