American art pottery collectors have their own terminology to describe the condition and grade of a particular piece of American art pottery. The following offers generally accepted definitions of common art pottery terms.
Mint condition implies that a particular piece of art pottery is in “as made” or “like new” condition. Mint condition items are always free of chips, cracks, repairs, or similar damage or wear. Normal crazing and typical factory flaws that are seen on Roseville, Rookwood, Weller and other American art pottery does not exclude a piece from being classified as mint. In all cases, if these factory conditions are beyond the norm typically seen on art pottery they should be mentioned in the description.
Crazing is the fine crackling you often see on most glazed art pottery. Crazing is in the glaze and is not detectable when you rub you fingernail over crazing. Art pottery crazing occurred during pottery production when the clay body and glaze cool at different rates.
Crazing is a very common condition with virtually all glazed art pottery. It is very uncommon to find entirely uncrazed examples of Roseville, Weller, Van Briggle and other American art pottery. Rookwood although also often displaying some crazing faired better than most in producing uncrazed art pottery. Normal crazing or crazing that can’t be seen at arms length does not typically affect the value of Roseville, Weller, Van Briggle, Teco, Owens and others. Rookwood collectors will often pay a premium for uncrazed examples. Most reputable art pottery auction houses state right in their terms of sale that buyers should expect crazing on all glazed or painted art pottery.
A glaze chip is simply a chip, which does not impact the clay in any way and simply involves flaking of the glaze. Glaze chips are common on the high points of hand-tooled pieces such as Grueby, Wheatley, and similar art pottery.
Peppering is the minute black specks of carbon that is sometimes seen in white or light colored glazes. Peppering is a condition that can be seen in some examples produced by most American pottery companies including Roseville, Weller, Van Briggle and even Rookwood. Some Roseville patterns such as Primrose and Thornapple were much more susceptible to peppering than others. Minor peppering doesn’t usually adversely affect the value of piece.
A glaze scale is typically an area where the glaze has flaked from an edge or ridge of a piece of art pottery. A glaze scale can also occur on art pottery where the glaze is not adequately adhering to the pot. This type of glaze scaling can sometimes be seen on Roseville Rozane, Weller Louwelsa, and Owens Utopian where the pots have loose crazing or have been cleaned with harsh chemicals.
Glaze skip or glaze crawl
Glaze skips or crawls are areas where the glaze did not completely cover the pot leaving areas of exposed clay. Glaze skips are seen more often on early arts and crafts pottery such as Grueby, Hampshire, and Van Briggle.
Glaze pops occurred during firing when air bubbles reached the surface of the glaze and burst.
A factory firing line is a crack that occurred during firing of a piece of pottery. Firing lines are not damage that occurred after production. Firing lines typically occurred at weaknesses in the clay body. Particular areas susceptible to firing lines include hanging holes on Roseville wall pockets and hanging baskets, and the corners of Rookwood, Weller, Van Briggle, and other art pottery.
A kiln flaw occurred when pottery in the kiln came in contact with either another piece of pottery or the kiln wall. A kiln flaw or kiln kiss often resulted in glaze loss on one pot and possibly excess glaze blips on the adjacent pot.
Factory glazed chip
A factory-glazed chip is a chip that occurred on the piece prior to firing and glazing. Factory glazed chips are not post-production chips that have been subsequently repaired and reglazed. Factory glazed chips or mold flaws are more common on Roseville, Weller, and Van Briggle than other American art pottery such as Rookwood pottery.
A hairline crack is a crack that goes into or through the clay body and can be felt with a fingernail. In some instances, new collectors and less than reputable dealers will refer to hairlines as crazing. If the crack is into the clay and is detectable with a fingernail it is not crazing. Pottery such as Roseville, Weller, and Rookwood are susceptible to hairline cracks from minor abuse. Other pottery such as Van Briggle is less likely to be found with hairlines.