The dazzling patterns on cut glass bowls are created with a series of grinding wheels made of stone or edged with diamond chips. The craftsman starts with a plain bowl, called a blank, that is either pressed or blown to create its shape. This blank glass has a high lead content, making it more stable and giving it a distinctive ring when flicked. The pattern is drawn onto the bowl and then ground out. Identifying cut glass bowl patterns starts with determining the manufacturer, glass quality, blank type, and the pattern motifs.
Determine the blank type from which the bowl is cut. Lightly touch the deepest part of the bowl's pattern. This area is slightly raised when the bowl is cut from a pressed blank and smooth if cut from a blown blank. Some manufacturers only use blown blanks, so you can narrow the search by determining the blank type.
Determine the glass quality. Hold the bowl up to a window during the day and look through the uncut areas. Quality glass is perfectly clear, without distortion of outside objects. If the glass is high-quality, you can narrow down your search to a reputable glassmaker.
Identify the pattern motifs. The pattern comprises a combination of shapes, lines and relief. Write down the recurring shapes such as fans, flowers, a chain of hobstars, or checkered diamonds or squares. There may be several motifs or only one that is repeated with glass colour variations.
Look for the manufacturer's trademark or signature. Many cut glass makers apply a trademark sticker or adic-stamp their logo on the piece.
Determine the signature cuts and patterns. Look at the rim. Glassmaker Pairpoint cuts its rims with a series of crescent-shaped scallops; on Clark bowls, the hobstars fill the diamonds in which they are cut; Sinclaire places moons below the rim line in many of its patterns.
Obtain the manufacturer's catalogue once you have determined the quality of the glass and identified the manufacturer and the motif (for example, a blown blank of high-quality glass with a pattern of recurring hobstars, a mirror star on the bottom and a ripple-cut rim made by Tuthill). Use the manufacturer's catalogue to identify the pattern.