Craftsmanship In Clay : Glaze Application (1949)

glaze is a thin clay pieces at high temperatures it enhances the piece by color and texture and provides a surface that is easily clean glaz is usually applied to a bisque piece one that has been permanently hardened by firing it can be applied by one of four methods dipping pouring brushing or spraying before glazing the surface of the piece must be prepared by thorough dampening to remove dust and prevent too thick a glaze coating the liquid glaze is composed of powdered ingredients mixed with enough water to make a workable glaze slip its proper consistency depends on the method of application and the paracity of the piece thing completely covers every detail thin spots left by by the fingers must be carefully touched up the pouring method may be used for pieces too large to dip such pieces are usually dampened by sponging the sponge should not be wet enough to drip because a saturated bisque surface will not hold enough glaze on the other hand a dry surface would absorb the glaze too rapidly making the coating thick and uneven particular attention is given to the angles formed by the foot Rim the handle or the lip pouring is the only practical way of applying glaze to the inside of a deep piece quick rotation completely coats the inner surface the remaining glaze is to be used in coating outside usually a single poured coat is sufficient only the surfaces easily reached are coated by pouring the handle and other bare spots are touched up later in Touching up the glaz is flowed on from a fully loaded brush the brushing method requires a minimum of equipment and glaze however Special Care in application is necessary a fairly dry brush is used to pre-coat any decorative details such as these incised lines a thin coat of glaze stippled into the design prevents air pockets under the next coat air pockets will cause pin holes in the fired glaze a fully loaded brush is used when coating the entire surface brush Strokes should overlap in several directions to avoid bare spots that would cause blemishes The incised Potter's Mark should be stippled like the design to prevent air pockets quick but careful application prevents drying between strokes and results in an even coating two full coats applied in quick succession are sufficient for the under side a stilt protects the damp glaze coating during the final touching up greater richness will result from an additional coat on the upper side many effects can be obtained with colored glazes applied by brush the appearance of any raw glaze seldom suggests its Rich final color this final color depends on the ingredients in the glaze and is developed in the firing glaze slip should always be well stirred to assure even consistency when applied by spraying it is also strained to remove any particles which might clug the spray gun the top of the gun must be screwed onto the cup tightly to prevent loss of air pressure in spraying as in all other methods dampening immediately before the glaze application is an important step the present colors of this piece with its decorative design will be retained by using a glaze which is transparent after firing the hrer should be clean to avoid spotting the piece an exhaust fan is necessary to carry away the injurious glazed dust the spray gun should be tested to be sure it's working properly before application is begun after the area with within the foot Rim is glazed the coating is applied in a continuous spiral down to the Outer Rim the gun is held close to the piece and the spray is directed at right angles to the surface when the glaze no longer glistens the piece is dry enough to be turned over but still damp enough to require a stilt to prevent damage to the coating merely covering the surface with a spray of glaze is not enough the first coat must be built up to the proper thickness indicated by a glistening appearance to avoid an excess of glaze in the center of the piece a brush-like motion is used when the first coat is completely dry the second coat is applied with the gun held at a much greater distance depending on the effect desired three to six coats may be applied if they are spaced with proper intervals of drying a porous granular appearance indicates correct application a glaze coating is usually thinner on the underside of a piece removing glaze from the foot Rim before firing will prevent stilt scars on the finished piece a stiff brush may be used in cleaning the foot Rim however the last traces of glaze can be removed only by sponging a fettling knife can also be used to scrape away most of the dry glaze the glaze coating on the inside and outside edges of the foot rim should be carefully beveled sponging away the remaining glaze provides a professional finish when there is no foot rim cleaning is optional if the bottom is left glazed small scars caused by the stilt during firing are unavoidable unfired glazed pieces must be handled with great care to avoid damage to the fragile glazed coating each piece should be examined closely for glazed defects which must be corrected before firing blemishes become permanent after firing for example too much glaze or failure to clean the foot Rim will cause plate pins or stilts to stick to the piece these thin spots left by brushing could have been covered by a second coat too thin an application may cause unpleasant roughness an excess of glaze will run down leaving a pool in the center of the piece and dust on the surface or too thick a coating will cause this defect known as crawling thorough preparation skillful application and precise finishing are essential in each of the four methods of glazing beautiful and satisfying pieces can be made if care is given to every detail of fine craftsmanship