Thursday, 1 January 2015

Generic discussion of my ceramic method

(developed so I can hotlink to this rather than retyping it each time)

General Technique:
In the late middle ages to the renaissance, a number of centers for production of highend earthenware existed across Europe. While each area had their own style, techniques and motifs often travelled along the trade routes. Generally, earthenware plates and bowls would be moulded, fired and then ceramic artists would glaze them typically with tin based glazes. These processes were usually handled by different specialists. (the V&A website has some detailed information related to earthenware production).

For all my work I have used commercially produced bisque. I have then glazed it with commercial (and modern) glazes. To achieve a solid colour, the under-glaze must have three layers painted on. This takes some time, but is important to prevent thick lines or splotchy colours. Where white decoration is required, it is either left blank or the coloured glaze is scratched back with a wooden skewer to reveal the ceramic or a layer of white glaze underneath. This is a period technique as shown by the fine lines on this 16th century Spanish pharmacy jar (1) where the cobalt glaze has applied then carefully scratched off. A clear over-glaze is then applied before firing which I get done at a professional service.

I feel my approach is justified as I don't own the equipment to produce my own bisque and while I have dabbled in glazing, I don't own a kiln either so can't risk ruining other peoples work with my experiments. I'm also aware that many of the lead based glazes use din period may not be appropriate for items people wish to eat from. A side benefit of the professional firing service and commercial glazes is that the items I produce are microwave and dishwasher safe!

The bisque I purchase comes in a limited set of shapes. This restricts the items I can do and how closely I can replicate items due to changes in scale or shape. For each of the items presented here, the design drives the bisque choice when then modifies the design application.
Typically the extant items I replicate are tin-glazed earthenware which is pottery which is coated in a glaze containing tin oxide. This leaves an opaque white base upon which metallic oxides and other glazes are painted. The main difference between my work and that of the workshopss of the middle ages is that I use commercial glazes. These glazes come pre-mixed and are usually a consistent colour. They also contain no toxic substances and due to the over-glazing process result in a product that is dishwasher, microwave and most importantly food safe. Many medieval items utilise a lead based glaze as it can create a higher intensity in colours like red. Needless to say, I doubt my items would be as useful if they weren't functional as well as pretty. The other major difference in the glazing is my lack of lustre. Lustre ceramics involves utilising a glaze containing metallic oxides which leaves behind a shiney lustre once fired. The technique was first developed in Iran before spreading to Egypt and then onto Europe. In the renaissance, Spain was the center of lustre-ware production featuring Moorish designs and pseudo-kulfic inscriptions. The line of commercial glazes I use doesn't contain a lustre products so at this point I cannot replicate this form of ceramic.


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