Leaded glass, commonly known as crystal, can look and feel similar to regular glass if you do not know what to look for. Many people don't even realize there is a difference. Leaded glass is made up of the same basic components as manufactured glass, with the addition of one important ingredient: lead oxide. This chemical is used by glassmakers during firing as a quality enhancement. Leaded glass is used for more detailed glassware, and can usually be distinguished from ordinary glass based on physical properties like cut and clarity. To properly determine whether a product is made from leaded glass or regular glass, you will need to follow these steps.
Step 1 - Judge Clarity
Due to higher lead content, crystal has high optical clarity, often appearing clear or even white, hence the term "crystal clear." Glass cannot achieve the same level of purity, therefore glass objects often have a yellowish/greenish cast or tint instead.
Step 2 - Compare Cuts
The addition of lead to glass not only enhances clarity it also softens the glass, making it easier to cut. Unleaded glass cuts will be rougher and more obvious to the touch, whereas in crystal the cuts have a more refined texture and precise look.
Step 3 - Compare Weight
The addition of lead to a glass object will increase it's molecular density, causing the crystal to be noticeably heavier than glass. Hold your glass object in one hand and the crystal object in another. The crystal will be heavier and denser than the glass object.
Step 4 - Tap the Brim
When struck, the crystal will transmit a clear ringing sound or "ding." Tap the crystal object and test its sound clarity. The clearer the ring, the higher the lead content. Tap a glass object and you will notice the glass only makes a dull thumping sound. This is because the crystal is bonded together more closely due to the lead content and therefore absorbs less energy than ordinary glassware.
Step 5 - Hold in Light
The simplest way to tell the difference between glass and leaded crystal is to hold each object up to a light source. Crystal is well known for its refraction and its inherent ability to bend light. If you hold an object up to the light and it sparkles and throws the light into a dazzling pattern, this object is made of leaded crystal, not regular glass.