Glass Tips 101.

Clear Glass Prior to the 18th century, is Usually Discoloured Due to Manufacturing Difficulties During the Early Years of Glass Making. 

 

To help Authenticate Clear Antique Glass, try using a small Piece of Modern Glass as a "Control" for Comparison.

 

Under Ultraviolet Light, the Old Lead Glass will Appear Blue-Purple, Newer Soda Glass will Emit Green-Yellow Light. 

 

  • The pontil mark on glass can help reveal its age, glass made during the 18thc will have a pontil mark as at that time, there was no known way to remove it, grinding techniques developed in England and Ireland in the late 18th to early 19th centuries enabled glassmakers of that time period to polish/ grind off the pontil marks.  (Note: this information should only be used in conjunction with other indications of age as the presence or absence of a pontil mark is only an aid to dating and not a guarantee) 

  • Another characteristic of the age in glass can be seen on the rim and/ or foot, even shapes and thickness usually indicates the piece is modern. 

  • A "lopsided" appearance in the blown (free-blown) glass is also a suggestion of age, as are fine ripples over the surface of the glass. 

  • Proportions of the various types of glassware from different periods are documented and are therefore helpful in distinguishing genuine pieces from reproductions/fakes. 

  • 19th century enamelled glass colours are usually brighter and more solid than their earlier counterparts. 

  • Gilding (on glass) during the 16th-17th centuries was usually applied in layers and you will generally find pieces from this period with only traces of gilding left. Later gilding on glass has a flat, regular appearance. 

  • 18th-century "diamond" engraved glass can be identified by its shallow and highly skilled engraving, look for (engraved) lines that are not deep, but are somewhat ragged and slightly broken; in comparison, wheel engraving produces "hard" lines. 

  • In the 19th century engraved glass look for a design that is well-drawn and detailed,  the glass body should be of high quality. Almost all 19th century engraved glass was done using a copper wheel. 

  • Again, style in engraved glass can be a clue to age as the engraver's style changed during the late 18th century to the 19th century. 

  • The quality of engraved pieces will vary considerably; and high quality, signed pieces are very valuable, the value will depend upon the subject matter, quality of engraving and of course, condition! 

  • If you collect 19th-century Bohemian glass, look for rich, solid colour with a thin outer layer; the glass body should be heavy and of high quality.

  • Acid etching began around 1830, with this 19th century glass look for a satin matte/ or frosted design that appears to be "on the surface" (as opposed to a design that looks "scratched into the surface"), again the body of the glass should be of high quality, with the pontil ground (or smooth). 

  • Early acid-etched pieces can be distinguished by a pattern outline made by acid-etching and the solid parts of the design made by (hand) engraving. 

  • The most desirable acid-etched glass are large jugs, decanters, and goblets decorated in classical designs. Less desirable designs badly drawn flowers and geometric designs. 

  • Acid-etching was also used to produce "faux" cameo glass, (true cameo glass is hand-cut), pieces using the acid technique can be distinguished from the true cameo pieces by their softer outlines and a poor background finish. 

  • Glass became increasingly clear from the 18th through the 19th centuries as manufacturing processes became more controlled. 

  • Much coloured English glass found today will date from the 19th century, with blue, amethyst and green being the most popular colours. Be aware that many companies continued to mass-produce inexpensive coloured glassware to the 1920s. 

  • American coloured glass was made from the end of the 18th century. 

  • There are 4 methods of engraving on glass, a diamond point, wheel, stipple, and acid. Diamond-point engraving was used in the 16th century, wheel engraving (around the 17th c.) was first made by foot-powered treadle machines using a copper wheel, later (after the 1830s) power machines operated the wheel, stipple engraving used a diamond needle which created a series of small lines and dots to form the design, this technique originated in the Netherlands, Acid-etching is the most recent form and was widely used during the 19th century.

  • It is difficult to determine the date of engraved glass,
    however, "new" engraving has a rough, chalky appearance. To detect this, place a white piece of cloth inside the piece...if the engraving appears greyish the engraving was done at least 100 years earlier as age and wear tend to tone down the harshness of engraving and this wear will give a smooth, satin sheen to the flat surfaces of the design. 

  • To determine if a piece is acid-etched or wheel engraved, (under magnification) look for small individual strokes in the design that are left by the engraver's wheel, an acid-etched piece will have an even finish with a sharply defined design outline. 

  • Beware...during the second half of the 19th century, several German glass houses made copies of Roman, Venetian, and medieval German glass. Additionally, in England, there were many imitations made of 18th-century drinking glasses. There are also many 20th century fakes of 18th-century glass! 

  • In attempting to detect fakes, check the colour and texture of the metal, the manufacturing method, the proportions, the decoration and always check for signs of wear. 

  • Much 18th-century glassware (prior to mid 18th c.) has a dark Gary, yellow, green or blue tint...to check for this compare the "antique" piece with a piece of clear, modern glass that you carry with you, and look for the blue-purple colour under a black light. 

  • Another good indicator of date can be seen in handles (of jugs, etc.), check the method of application of the handle, prior to about 1860, the main junction of the handle was at the top, after the 1860s the handles became more securely attached and the main join was at the base. 

  • Look at the foot of old glass for signs of wear...here check for scratches made from years of use. Faked age scratches will appear even and sometimes run in the same direction, genuine "age scratches will be irregular in depth and size. 

  • The Golden Age of cut glass (also known as the Brilliant Period) was from 1830, later, when steam power was available, there was more precision in the design. 

  • To determine if a piece of glass is flint or lead as opposed to soda-lime glass, tap the glass and listen for a resonant tone, you should hear a clear "bell-like" ring. (Note: sometimes the shape or form of the piece will preclude hearing the bell-like ring, so this test must be used in conjunction with other characteristics of lead glass). 

  • Flint glass has a high degree of internal reflection and is usually more brilliant than soda-lime glass, it is also relatively heavier than soda-lime. 

  • Newer (improved) Soda-lime glass has neither the tinkle of old soda-lime nor the bell-like ring of flint glass. The improved soda-lime glass has a dead, dull thud. 


 

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