Month: April 2013

Early Plastics : Identifying Lucite

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Lucite was a popular early form of plastic that is still used today.  While transparent in its natural state, lucite can be dyed many colors, molded and imbedded, so comes in a wide and sometimes wild variety of colors and looks.  It is found transparent to opaque.  In vintage times, it was used to make everything from plastic toys to jewelry.  Colorful versions of jewelry are often mistaken for catalin plastic which could also be made in many colors and textures.

Identifying antique plastic:

Lucite has a slick feel and is fairly light in weight. It is lighter than catalin.

If you put it under hot water, rub it vigorously or poke a hot pin into it it will have no smell. Catalin, bakelite and celluloid have chemical smells and casein smells like burnt milk.

If it’s transparent or transparent with objects embedded in it (plastic pieces, flowers, coins, etc) it’s lucite.

The following are examples the various styles of lucite.

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While naturally clear, lucite can be dyed and molded

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moonglow lucite has a unique glow-from-within quality. Used for jewelry.

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transparent, molded bracelet

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The ever popular confetti lucite, with confetti or shavings embedded within the plastic.

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confetti lucite button

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transparent lucite with embedded plant piece

granite lucite with embedded material to give a granite or marble-like look.

granite lucite with embedded material to give a granite or marble-like look.

Identifying Precious Metals: gold, silver and platinum

As precious metals can have high monetary value, this is an area where getting a educated second opinion can be a good idea for a beginner. A jeweler or avid collector can identify and grade the metal for you. However, the avid collector can make a fair judgment about type and quality of previous metal.

There are both scientific tests and more informal ways of identifying gold, silver and platinum. The first part of this post looks at the quick-and-dirty, unofficial in the antique store methods, methods. The second part of the chapter will show the scientific acids tests.

* * * *

Informal quick tips for identifying gold, silver and platinum 

* Look at different metals to get an eye for the look. Though somewhat similar in color, gold looks different than brass and copper. Silver looks different than pewter and aluminum. An experienced eye is helpful.

Gold

* Gold is a shiny yellow color and does not corrode or rust. Very old gold can look shiny brand new. Gold is both very soft and heavy.

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an ancient gold coin can still by bright and shiny

* Gold is not attracted to a magnet. This is not a definitive test as some other metals are also not magnetic.

* Many people do the simple test of running gold along unglued porcelain tile. If the mark that is left is yellowish-gold the metal is real. If the mark is black the item is not.

* Gold is usually that yellow gold, but it can come in different tint or color variations depending on the allow. This includes white gold which almost resembles silver or platinum.

* Is 2.5 -3 on the mohs hardness scale

Silver

* Silver is, well, silvery colored. It looks slightly different than steel, though steel kitchen utensils are often mistaken for steel.

*Silver is not magnetic. Some but not all steel is magnetic. A refrigerator magnet is excellent at identifying many steel kitchen utensils and bowls.

*
Silver has a naturally dull finish. Only silver-plated is shiny. Steel is often shiny. 

tarnished silver

tarnished silver

* Steel is colder than silver. Touch it to the side of your face. 



* Rub a clean, white polishing cloth over a silver piece. Real silver and silver plate will turn the cloth black.

* Is 2.5-3 on the mohs hardness scale. This is soft. Softer than steel and glass.

Platinum

* Platinum doesn’t tarnish or degrade, including very old pieces.

* Platinum is the heaviest precious metal, noticeable heavier even than gold.

* Platinum is not attracted to a magnet. Some but not all steel is.

* Is 4-4.5 on the mohs hardness scale

*** Hallmarks

Precious metals often have hallmarks on them, identifying the type of metal, percentage of precious metal (14kt, 24kt, etc), era and where graded. As this is a full topic in and of itself, it will be discussed in a later post. Also, hallmarks can be forged so you can’t rely just on them.

*** Precious metals acid testing kit

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acid test kit with clearly labeled bottls

There is an inexpensive and use to use kit to testing precious metals that use acids to test the metals. These kits can be bought at amazon, ebay and other places. The kit includes the testing acids in little eye drop bottles, a testing stone and instructions. You don’t have to be a chemistry expert or have lab experience to do the tests. Be careful with the acids as they can stain or worse your hands, and keep it away from your eyes.

Testing Gold with the acid kid:

There are clearly labeled bottles of 9kt, 14kt, 18kt and 22k testing acids in the kit.
The process is simple, scratch or rub the metal in an inconspicuous area onto the testing stone so there is a little streak of metal. 
Place a drop of the closest acid to the karat you estimate the metal to be.

If the acid dissolves the metal it’s less then the karats on the bottle and you should try again with lower level acid.

If it dissolves the metal slowly, it’s possible you would have a bit less then the karat of the acid in the bottle.

If the metal stays it’s most likely the karat of the acid in the bottle.

 

Platinum

Should stay and not dissolve under the platinum acid.

 

Silver:

Make a ittle metal streak on the stone, apply a drop of the acid and white fa bit or a color to appear.

0.999 pure silver will turn bright red color

0.925 sterling silver will turn dark red color

0.800 silver will turn brown color

0.500 silver will turn green

* * * *

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Identifying Stone in Sculpture and Construction: marble, granite, sandstone, limestone, alabaster and soapstone.

The following is an identification guide to several standard types of stone used in sculptures, carving, building construction and similar. The types covered are marble, granite, sandstone, limestone, alabaster and soapstone.

*** Marble

Marble is a  high end stone used to make everything from Michelangelo sculptures to mansion steps and walls for mansions. Marble is limestone that was heated longer  and transformed in the earth’s crust. It is often mistaken for granite, and visa versa, as the two have the same general look, weight and are used for similar purposes. Luckily, they have several distinct qualities that help tell them apart.

Polished marble is smooth and silky with a highly reflective surface. You can often see your face reflected. If the polished and clean surface has roughness or bumps, it is not marble.


Marble is at least two colors or tones and has a distinct pattern. The pattern grain that runs through it, made up of lines and waves that create a jumbled pattern. Some of the lines may smudge and swirl. If the marble has a speckled or crystal-like markings, then it is more likely to be granite . The colors in marble include pink, black, white, greenish, red and cream.

The colors are soft shades, rather than bright.

marble lines/grain pattern

marble lines/grain pattern

Marble is very heavy, but relatively soft with a Mohs scale hardness of 3-4. It can be cut by a steel knife. Granite is much harder and cannot. If you cannot cut it with a knife, it is probably granite.

Vinegar will make bubble fizz, whereas granite will be unaffected. The bubbles can be very small so use your magnifying glass to see.

Splash water on the material surface . Marble does not absorb water and water will pool.

If you put an acid liquid like vinegar or lemon juice, marble will react producing fizzing bubbles.  The bubbles are very small, so you might need a magnifying glass to se it.  Granite does not react.

*** Granite

Granite is a commonly stone used in construction and is often mistaken for marble. Granite is made up of crystal and was heated much as lava is.

Granite is heavy like marble, but much harder. It is 7 on the Mohs hardness scale. Unlike marble, it cannot be scratched by a steel knife. Unlike marble, granite doesn’t react to vinegar, lemon juice or other acids. Granite generally has a more sparkly, granular pattern, as opposed to the fluid lines of marble.

speckled granite design

speckled granite design

* * * Alabaster

Alabaster is famous as a milky white mineral that can be translucent if carved thin enough.

There are two types of alabaster. One is gypsum, which is used today. The other is calcite, which was used in ancient times including by the Ancient Egyptians.

The two kinds share the same white appearance, but are distinguished from each other due to a difference in hardness. The gypsum kind has a Mohs hardness rating of 1.5-2 and be scratched with a fingernail. The calcite kind has a Mohs rating of 3. It can’t be scratched with a fingernail but can be scratched by a knife

Hydrochloric acid makes the calcite alabaster fizz and bubble, but does not effect gypsum alabaster.

Ancient Egyptian alabaster heads

Ancient Egyptian alabaster heads

*** Sandstone

sandstone color layers

sandstone color layers

Sandstone is sand turned to rock over time. It formed when grains of sand become cemented together. Sandstone is opaque, with a dull often rough luster. It is usually tan or yellowish, though can be found pink to dark red, and even sometimes blue and green Sandstone is identified by distinct wavy color or tone patterns from how the sand lawyered. Horizontal lines through the stone, indicating the layers, shows it is sandstone not limestone. Limestone is uniform in monochrome (one color).

The hardness varies with sandstone but is often around 7. If you break a part off with a hammer it will crumble with lots of sand. Limestone doesn’t crumble.

* * * Limestone

Limestone is is often mistaken for sandstone, but, unlike sandstone, is one of solid color and much softer (Mohs 3). It can be cut with a knife. Vinegar and hydrochloric acid makes limestone fizzle and pop as it dissolves. Sandstone would be unaffected.

* * * * Soapstone

Soapstone is an attractive stone that has long been used for both practical and decorative purposes. It comes in different colors, including green and pink. When held to the light, soapstone has a smooth, greasy, silky, milky luster. If thin it is transluscent. It is cold to the touch.

shiny soapstone carcing

shiny soapstone carcing

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