Crystaline Blue/Purple Galze- recipe from Linda bloomfield book.
Temperature fired@ cone9/10, 1280c (mmu stoneware)
The image on the left shows the colours on Almington, ivorystoeware, terracotta and porcelain clay bodies.
It doesn't seem to be behaving anything like the image provided by the artist. the surface is dry and no visuals of purple colour coming through. The colour blue is very dark and not textures or speckles are to be seen.
Clearly, my sample looks nothing like the artist provided sample.
Possible reasons:
1) My test samples were fired to cone9/10 rather than the suggested temp. This could have made the glaze mature/melt more reacting in the way it has.
2) addition of the oxide was not accurately done, I used scales that didn't go to .01 (two decimals) resolution.
3) Not applying the glaze evenly onto the surface- my process of application was dipping for 3secs.
MY THOUGHTS:
Though the glaze looks nothing like on the sample provided by the artist, I feel this glaze worked out in its own unique way for me. The drippy and melting effect on the surface is something i really enjoy. It hold a textured effect but is a smooth surface.
The glaze is a matte surface, and not shiny/glossy surface, which makes these objects all the more special.
These were objects have glazes applied differently onto them, but the final look makes them look similar. i don't think adding the glaze a different way has any sort of effect for this type of glaze, as it is a textured looking glaze.
FURTHER TESTING THIS GLAZE:
left: two rows are tests that are fired to cone8, right: row has been fired to cone9 temperature.
There is a slight change in colour, the blue seem to be a little lighter in colour. again no purple speckles showing through.
Changing recipe- found a recipe with tin oxide rather than zinc. this will provide a white background making the colour pop, zinc too is a opaque colourant but isn't commonly used as a white colourant compared to tin oxide.
Vertical surface, ivorystoneware body, cone9/10, dipped application
Cone 9/10, poured application, curved form, ivorystoneware body
Massive change in colour with the altered recipe. the colour blue is much paler and lighter making the surface shimmer and not dark on thin application.
Almington clay, same glaze as above.
very matt surface could be because of thin application, glaze applied through pouring on the inside and brushing on the exterior.
Conduct= An accurate colourant test 0%, 0.25, 0.5, 0.75 and 1%
Ivorystoneware, Almington and Porcelain clay bodies.
Grey/Stone glaze- Linda Bloomfield:
Before: 3secs dip, with cobalt.
Before: 3secs dip, without cobalt.
After: tested on: Almington, ivorystoneware and porcelain
After: tested on: Almington, ivorystoneware and porcelain
This glaze is meant to be a Crystalline grey-blue glaze, with speckles formation. But nothing seems to be forming on the surface.
The recipe calls for cobalt addition, I have tested the glaze base, with and without the addition of cobalt. The glaze isn't meant to be blue so I don't understand why add cobalt?
Reflection- The grey didn't show through, possible because it needs to be dipped in for longer. on careful observation on thicker areas hints of grey/textured surface seem to be forming.
Without Cobalt: on lighter surfaces it has turned into a pale brown colour. like a sand colour. i would definitely say the sample needs to be in the glaze for longer, so that the glaze is absorbed properly onto the surface.
With Cobalt: lighter clay bodies, the blue seems to be very apparent. it is a nice blue but not what I'm after. across both almington samples on thiner application it has turned into a stained brown colour.
Not a successful glaze mix up.
thicker application test-
brushing glazes thickly to see if it makes a difference on the surface, clearly visible from the above test 1 brush application compared to 5 there is a huge difference. On just one brush application its dark and not even. the clay body can be seen through. but on five brush marks its consistant and not uneven. also holds a nice pigment. successful and useful test results.
CRYSTAL GLAZES:
The surface quality of these glazes are very textured, theres flow within the glaze adding pattern and movement to the glaze. This makes the surface look like a screenshot of the melting stage within the kiln, which is why i like these types of glazes that aren’t a simple still surface but visually communicate far more i.e process journey.
Left- use of potash Feldspar.
Middle- use of Spodumen Lithium
Right- use of soda feldspar.
CLOSE UP IMGES OF INDIVIDUAL GLAZE TEST SAMPLES:
first test results- no colourant, second/third- addition of colourant and on two different clay bodies.
potash feldspar, almington clay body
soda feldpspar, white clay body
lithuim feldspar, white clay body
OXIDE BLEND INTO CLAY TEST:
Addition of 1,5 and 10% oxide to ALM and IVS clay testers( 20g each)
Clear glaze over the top, fired to Stoneware temperature.
Before: Batch 1
Bisque fired batch 1
Before: Batch 2
Bisque fired batch 2
Glazed samples- front side (shiny sides)
Non glazed side- stoneware fired (not shiny)
Reflection- Conducting this experiment was a really useful test, not only did it give me a colour indication of each of these oxides but I found out adding excessive amount of oxides can make the clay flux. Such as Manganese and Copper adding more than 5% will make the clay body flux in the kiln at this temperature. Also, the surface quality changes from flat to rough and bumpy.
Vanadium Pentoxide is another really interesting oxide high toxic in large qualities not is recommended not to add into domestic wares. However, the colour range and natural pattern the oxide can form are so unique. Similar to this oxide,in providing a unique surface are oxides rutile and titanium. Both of these create visually appealing surfaces and can be used on domestic wares. Rutile is contaminated with iron hence the interesting surface with speckles. Titanium is a purified version of titanuim and it still give unique patterns. Both of these ingredients are best reacted with the combination of other materials within the glaze.
IRON BLUE GLAZE:
This glaze only has red iron oxide in the glaze and the outcome is blue with blue’ish around the rims where the glaze breaks or is less compared to the rest of the surface.
The reason for this blue is due to the combination of bone ash material and red iron= the combination of the two are chemically bound to make up a blue colour. The quality of the glaze is textured and not blended still which adds interest to the surface.
Through the above test samples, I would say a thicker coat of glaze is necessary, for colour to appear on the surface. This glaze is fired to stoneware 1280c/ cone 9 temperature.
SPECIAL FIRING REQUIRED- BUT WORKS EQUALLY WELL AT CONE 9/10.
BLUE/ GREEN SPECKLY GLAZE.
This is another grainy consistency glaze.
The recipe calls for FFF feldspar- 18.10% to which I have mixtured up (12 potash feldspar+ 6.1 soda feldspar)
PINK GLAZE
Interesting how something that’s supposed to be pink is turning green at oxidised temperature.
Reasons for this behaviour could be that the fired temperature (cone9/10) is really high for the desired appearance. The feel of the surface is satin and colour (green) is best seen on ivorystoneware clay. The glaze also provides a speckly surface, this is probably from the rutile present within the glaze.
Glaze on almington body= Olive green colour and brown on edges.
Bubbling on thicker application but this could be the almington clay which does bubble from being fired to high temperature- releasing gas which result in bloated effect.
Due to the satin quality of the surface it is not ideal to add this glaze on functional/ domestic ware.
Recipes does ask for it to be fired to cone8 with 25mins soak time.
Below samples have been fired to cone 8 with the soak time.
The series of samples are a test from 0% - 15% to see the exact point of colour change and the colour effect on almington and ivorystoneware.
ALM and IVS clay body , fired to cone 9/10 (no soak time)
ALM and IVS clay body, cone8 with 20mins soak.
Thoughts- through the two different temperature firing may not have been the most successful test results but theres a difference the samples with low temp and soak time towards the high percentages have hints of pink showing through bit strong and even appearance. Also, the surface quality is very matt/ dry which doesn't make an ideal food safe vessel.
16%, 17% and 18% red iron oxide addition, cone 9/10 (no soak).
Pink colour achieved best results on whiter clay body but not food safe surface. Also pitted surface because of the gas release from the glaze.
Wood ash+ charcoal contaminated glaze:
0-10% OXIDE ADDITIVES TEST:
ALM and IVS clay test tiles:
REASON: Observing the glaze reaction on the two surfaces, similarities and differences. How the oxides will react on surfaces with high and low iron content. The colours and textures that may appear on the surface:
Oxides used:
Titanuim Dioxide, Rutile, Illmenite, Red Iron Oxide, Yellow Iron Oxide, Black Iron Oxide, Calcined Yellow Occer, Manganese Dioxide.
Exploring the range of colours with increment oxide testing 0%-10%.
plain base samples (left image)
Reflection:
Through this experiment i have gained great knowledge on the colour palette available, which allows me to pick and choose the appropriate colour to add on the clay body.