Saturday, January 23, 2021

Digging deep into Scratch Blue Salt-Glazed Stoneware


This week’s blog is continuing our discussion of artifact types with relatively short periods of manufacture. These can be very useful in dating an archaeological site or feature. Today, we will look at another form of historic ceramic, salt-glazed stoneware emphasizing one form of decoration, scratch blue and its variations.

Salt-glazed stonewares were a common type of ceramic  in manufacture for a hundred year period between 1685-1785, with its peak in popularity circa 1720-1770 (Edwards and Hampson 2005:30, 34). As a durable and versatile ceramic form, salt-glazed stoneware began to replace tin-glazed earthenware and porcelains as common dining and tea wares in England. Their thin, dense paste made them light, durable and attractive and the distinct “orange-peel” like textured finish aids in  identification  of salt-glazed stoneware by archaeologists.

Examples of plain white salt-glazed stoneware with “orange-peel like” glaze from Fort Hunter.

The orange-peel like finish came about through the addition of salt to the glaze on the vessel while the kiln was at the highest temperature, thus giving it the name salt-glazed stoneware. These attributes included with different types of decoration, such as “scratch blue”, allow archaeologists to narrow down the period of manufacture

Example of scratch blue salt-glazed stoneware from Fort Hunter (36Da159)

Examples of scratch blue salt-glazed stoneware from Fort Hunter

Scratch blue, is called such due to the thin blue lines that are present on the ceramic body. Produced through a process of incising or scoring deep lines in the ceramic and neatly filling the lines with cobalt blue oxide and wiping the excess clean before firing, the finished scratch blue ceramic often has simple geometric or floral patterns. In production from 1744-1775, scratch blue was commonly used to decorate cups and saucers, pitchers and punch pots (Hume 1969:117). Due to this short manufacture date range, scratch blue salt-glazed stoneware can be a useful tool in dating an archaeological site or feature.

Scratch blue salt-glazed stoneware fragments from a tea cup recovered at Fort Hunter (36Da159)

 Another type of incised decoration on salt-glazed stoneware, called scratch brown, is an earlier form of scratch decoration with manufacture dates between 1720 and 1730, and are rare finds (Hume 1969:117; Following the same technique as scratch blue decoration, scratch brown uses iron oxide to fill the incised lines prior to firing.

One final variation of scratch-blue decoration found on archaeological sites today is debased scratch blue. Using the same manufacturing techniques as scratch blue stoneware, debased scratch blue used a more liberal amount of the cobalt powder and the excess not wiped off for clean striking blue lines. A later version of scratch blue stoneware debased scratch blue dates between circa 1765 and circa 1795 (Skerry and Hood 2009:106). 

Example of debased scratch blue stoneware from Fort Hunter. 

As can be seen through these brief descriptions even a small variation in decoration can make a difference on how archaeologists date and interpret a site. We hope this information has helped you see how small details can allow for a better understanding of past human behavior. Look forward to more descriptions of artifact types from Pennsylvania in future blogs. To see additional examples of ceramic types and other artifacts please visit our online collections.

What would the Farm Show be without our dugout canoe? 


Recently The State Museum participated in the Virtual 2021 Pennsylvania Farm Show with a special "virtual booth."  Check out a featured interview with Dr. Kurt Carr talking about our 800- year-old dugout canoe and our replicas at PHMC's virtual booth landing page



Hume, Ivor Noel

1969      A Guide to Artifacts of Colonial America. University of Pennsylvania Press, Philadelphia (reprint)


Edwards, Diana and Rodney Hampson

2005      White Salt-Glazed Stoneware of the British Isles. Antique Collectors’ Club, Woodbridge, Suffolk.


Skerry, Janine E. and Suzanne Findlen Hood

2009      Salt-Glazed Stoneware in Early America. Colonial Williamsburg Foundation, Williamsburg, Williamsburg, in association with University Press of New England, Hanover.


For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .