Have you ever wondered what’s the difference between the normal and so-called leaded glass?
We recover on average 5-7 Tonnes of non-leaded glass and 3-5 Tonnes of leaded glass each month. The majority of leaded glass we recover comes from old CTR (Cathode Ray Tubes) televisions.
How glass is made
The manufacturing process for glass depends on the type of glass, but as an example, window glass is made like this:
- In a commercial glass plant, sand is mixed with waste glass (collected for example from your yellow recycling bin), soda ash (sodium carbonate), and limestone (calcium carbonate) and then heated in a furnace.
- The soda reduces the sand’s melting point, which helps to save energy during manufacture, but it has an unfortunate drawback: it produces a kind of glass that would dissolve in water!
- The limestone is added to stop that happening. The end-product is called soda-lime-silica glass. It’s the ordinary glass we can see all around us.
- Once the sand is melted, it is either poured into molds to make bottles, glasses and other containers or “floated” (poured on top of a big vat of molten tin metal) to make perfectly flat sheets of glass for windows.
Remember, not all glass is the same, so separating glass by type is essential for recycling.
Difference between leaded and non-leaded
Now let’s talk about the difference between your ‘normal’ glass of wine and glass with added lead.
Originally discovered by Englishman George Ravenscroft in 1674, the technique of adding lead oxide (in quantities of between 10 and 30%) improved the appearance of the glass and made it easier to melt using sea-coal as a furnace fuel. This technique also increased the “working period” making the glass easier to manipulate.
Lead crystal can be identified by tapping your nail or a fork against the edge of the glass. If it clinks, it is glass. But if it rings, you have a crystal. Generally, the longer the ring, the higher the lead content.
Why do televisions contain lead?
Big CRT television can contain up to 2.2 kilograms of lead. It is mixed into the glass for two reasons:
- It acts as a shield against radiation generated by the electron gun and electron beam. The presence of lead is used in glasses absorbing gamma radiation and X-rays, used in radiation shielding as a form of lead shielding (e.g. in cathode ray tubes, where lowering the exposure of the viewer to soft X-rays is of concern).
- It improves the optical quality of the glass. Adding a small amount of lead to glass is very common when creating glass for lenses, and you may have also heard of leaded crystal. Optical quality is especially important at the front of the CRT.
Old monochrome black and white CRTs used to have lead in the front. Colour picture CRT Televisions only have lead in the back funnel section, with the front panel being lead-free, TGR separates the panel from the funnel maximizing recovery.
Leaded crystal health risks
Back in times, lead crystal glassware used to be used to store and serve drinks, but due to the health risks of lead, this has become rare.
One alternative material is crystal glass, in which barium oxide, zinc oxide, or potassium oxide are employed instead of lead oxide. Lead-free crystal has a similar refractive index to lead crystal, but it is lighter and it has less dispersive power. Meaning it’s less transparent.
The problem with lead is that very small amounts of it cause lead poisoning, so there is a large effort to keep lead out of landfills.
You can head over to Change.org to sign our petition and help us ban e-waste from WA landfills.
How to stay safe when recycling leaded glass
Our staff safety is our highest priority. One thing we do to ensure there is no workplace exposure occurring during our recycling process is testing our staff regularly.
This means every 3 months performing a blood test to check lead levels are within normal levels.
Why we shouldn’t put e-waste into landfill
The landfill acceptance criteria for lead in Western Australia is
- 2g/T for class 1 and 2 landfills (a lot of rural landfills are class 1 and 2),
- 20g/T for class 3 landfills,
- and 200g/T for class 4 landfills.
So if a television weighs 40kg and contains on average 2kg of lead it has a concentration of lead of 50,000g/T.
Not only is it bad to put your old television into landfill, but it’s also against the landfill acceptance criteria here in WA!
Thankfully, due to the National Television and Computer Recycling Scheme (NTCRS) items like these can be recycled free of charge.
All you need to do is find your nearest location drop-off point.