Glazes played an essential role in pottery. Without it, after being used a few times, the vessel would have acquired unpleasant odours and tastes due to the various organic elements which would have got into the pores in the clay and it would have been necessary to break the vessel to get rid of it.
The main procedures used to cover over the pores in the vessels include burnishing, engobe [slip], coating in pitch, glazing and enamelling.
Burnishing consists of smoothing the walls of the vessel by rubbing it, for example with a stone or bone. Pitch was once used widely, especially for vessels made to contain liquids. We have seen the procedure used as recently as the 1970s in the town of Alaejos (Valladolid). Although we have not actually seen either of these procedures in use in the Basque Country, this does not mean that they were not employed.
We have seen engobe used, but with a covering of glaze on top. Engobe is a layer of very fine clay diluted in water with which the vessel is coated. Engobe with glaze was widely used in the Basque Country, especially latterly, when high tin prices made enamelling uneconomical. Basque potters used this procedure to make pieces that looked like the better-valued enamelled vessels. The lead ore or "leaf alcohol", was mixed not with red clay, as had previously been common, but with white clay from Bernedo. Some potteries got the fine clay for the engobe from the iron mines of Bilbao.
The potteries of Zegama made their own glaze and enamel.
Glaze was used Persia and Asia Minor as early as 3000 BCE. From there it spread to Egypt, and thence to Phoenician, Cypriot and Roman potters. The Byzantine potters took up the procedure, and knowing the competitive advantage it afforded them, they kept it very secret, halting its spread to other places.
It eventually reached the Iberian peninsula with the Moors, and spread most quickly during the ninth and tenth centuries.
Like so many innovations, white enamel was first developed in Mesopotamia. It was the result of the Mesopotamian potters' attempts to imitate Chinese porcelain in the ninth century. The Chinese had been producing porcelain since the seventh century using kaolin and fine-grained limestone, which their horizontal kilns-more advanced than those of the West-allowed them to fire at high temperatures.
Like glaze, it was the Arabs who introduced enamelling to the Iberian peninsula in the twelfth century, although some researchers date its introduction as early as the tenth century.
The hand mills, used by our potters to grind the varnishes-one of the first and most important applications of the principle of rotation since the potter's wheel-appeared in the Basque Country in the second Iron Age.
Ignacio de Barandiaran says that the invention originated in the Mediterranean Near East (or perhaps Mesopotamia). This is the system that was systematically used in ancient Greece, whereas during the Roman era it as replaced by the water wheel for large-scale work.
Telesforo Aranzadi says that these mills were used in many Basque towns
where today they lie abandoned or are used as the base or capitel for posts. These mills, moew widely used to grind corn, were still employed almost to the present day by Basque potters.
We know that there were water mills for grinding varnishes in Galarreta, Elosu and Mendibil. In many cases they were simply flour mills which had been adapted to grind pottery varnishes as well.
The water mill in Zegama is an outstanding example of Francisco Jose Arregi's ingenuity and dedication. Not only was it used to grind varnishes but also to blunge-or mix-the clay.
These water mills are probably at least 3,000 years old, and originated in mountainous regions of the Near East.
The coloured decorations were added using copper oxide for the green, with cobalt oxide for the blue, and manganese oxide for browns and purples. The latter was used essentially to outline patterns in other colours, especially green. Green, brown and purple decorations were added in Teruel from the thirteenth century, in Muel from the late sixteenth century and in Villafuliche from the seventeenth century.
Blue, which was extensively used by the potters of Igeleta, Erentxun, Ixona and Vitoria-and undoubtedly in other Basque potteries as well-was introduced to the Iberian peninsula in the thirteenth century, and was first used in Muel, Teruel and Calatayud in the late fifteenth century.
The information comes from any extensive study on Aragonese ceramics published by Isabel Alvaro Zamora. It seems quite likely that use of these colours, like other pottery procedures, spread here up the River Ebro. We also believe that Haro was an important centre for spreading pottery techniques. It is possible that the etymology of the name Haro-(spelt "Faro" in mediaeval times) is the same as that of Faro in Asturias: Jose Manuel Feito say that the latter town, which had a long pottery tradition, was named for the Arab word alfar , meaning "pottery". The definite article, Al, was removed and the O was added".
I would cautiously hypothesise that the name Haro-previously Faro-might also have come from alfar?