Many times a glassmakers used a type of mark known as an acid badge. Many pieces of glass from the mid 19th century onwards have registration numbers. Earlier pieces may have a diamond mark to show that the glassmaker registered his design.
When trying to date your glassware you can look on the bottom for Pontil marks or Mold lines as those will help you determine whether the glass was hand-blown or manufactured. Below are the four main identifiable markings for antique glassware: embossed markings, maker's mark, pontil marks and mold lines.
One of the most important markings is the mould code. There are different ways to display the mould code. It can be represented in the form of alphanumeric numbers, digital codes or a dot code. The mould code is used to uniquely identify the glass container.
If there is no mark on the glass, there may be other signs that can help you work out how old it is. It may have mould marks, show the pontil mark of blown glass or have identifying characters within the glass, such as bubbles. All of these can help you find out more about your glassware with a bit of research.
Look closely at the glass edge: tempered glass will have a smooth, slightly rounded edge without sharp corners. Untempered glass has a sharp, unfinished edge. You may also notice small nicks or divots in the glass edge. Tempered glass has undergone intense heating and rapid cooling, so its surface is more durable.
You'll find up to three numbers on glasses frames, and they stand for the lens width, bridge width, and temple length. These numbers are written on the inside of one arm and may be separated by spaces or dashes.
These dots are often known as a "bottle code" or "glass manufacturer's mark." The specific meaning and interpretation of these dots can vary depending on the glass manufacturer and the industry standards in a particular region.
They identify the position that the mold in which the jar was made held on the glassmaking machine. Most machines would have from eight to ten molds, all making the same type of jar. The quality control people used the number on the bottom of the jar to identify which mold was producing bad jars.
The iron pontil bottle also has an open pontil scar. However, instead of the mark being colorless, the iron pontil bottle displays a reddish or brownish residue at the break-off point. The color is likely due to the color of the iron punty rod. Most iron pontil bottles were produced from 1845 through the mid-1860s.
Anchor Hocking basically used only three markings over its history. The original "HG over Co" was used from 1905 until 1937, the "anchor over H" used from 1937 until 1968, and the "anchor in the square" mark used from 1968 until recently. The company has started using a stylizied "anchor over H" in the last few years.
A pontil, a solid metal rod usually tipped with hot glass, is applied to the base of a vessel to hold it while the mouth is being formed. A pontil mark or pontil scar is the ring-shaped mark left on the bottom the piece when this rod is removed.
In most cases Viking used paper labels, not marks, to identify its products. Most of the labels on their glass are now long gone, leaving color as one of the few identifiers for buyers. Thankfully, the Company started publishing catalogs of its product lines in the early 1960s.
Pink and crystal (clear) are two of the rarest colors of Depression glass.
The black dots on a car windscreen or car window are actually called frits. Frits are pieces of black-painted enamel that are baked into the borders of the glass during the manufacturing process. Usually, they start out as a solid black panel at the edge of the glass before becoming small dots.
A pontil mark or punt mark is the scar where the pontil, punty or punt was broken from a work of blown glass. The presence of such a scar indicates that a glass bottle or bowl was blown freehand, while the absence of a punt mark suggests either that the mark has been obliterated or that the work was mold-blown.
Rainbow stains appear due to the change of the stress state in the glass, during the tempering process. Any uneven heating, cooling or uneven transporting of the glass on the rollers may lead to the anisotropic effect. The more nonhomogenic the process the bigger the effect.
Finding the Identification Code On Your Window:
This code is typically found etched into a corner of the glass or stamped or printed on one of the four sides of the spacer channel which separates the two panes of glass.
The first two digits represent the thickness of the glass and the last digit represents the tone of the glass: clear glass – MXX0; green glass – MXX1; bronze glass – MXX2; blue glass – MXX3. LAMISAFE: glass brand (Temperlite; Lamipane, etc.)
Any Signatures or Marks
Look to see if the glass has been signed or marked. Usually signatures are found on the underside of glass, but sometimes you can find one on the body.
Mid-century glass is the hottest collectible antique glass on the market today. Mid-century glass refers to the different types of glass made from the 1940s through the 1970s, ranging from Fire King kitchenware to milk glass dinnerware. There were many pieces of art glass made during this period.
Fashionable colors, patterns, and methods of decoration ebbed and flowed with each decade. The only way to tell if something might be of value today is through close observation. Small irregularities, like a glass knob at the bottom of a vase or cup, can indicate a piece was handmade.