By John P. Lloyd
When a customer (particularly a new one) needs to find out or figure out how much cerium oxide to put in the tank, there are two methods in use:1. The **“Dwight” method. This is whereby the machine operator can tell if the cerium in the machine is of sufficient quantity, either by looking at the slurry, or on his hand.. On his hand? Operators will put their hand in the cerium slurry, scoop some of the slurry out, and then see how much cerium stays in the creases of the palm. This is a crude approximation at best.2. Usage of a “baume” gauge. This is actually a hydrometer. A hydrometer is a glass tube that “floats” in the water.A Baume gauge is typically calibrated from 0 (zero) to 25. A reading of between 3 to 5 on this scale indicates the proper amount of cerium suspended in the water.The Baume Gauge, (available from Matodi) can be relatively expensive, and fragile. It is a tool that should be used on a regular basis; but it often gets misplaced, or broken. Or worse, the owner or manager locks the baume gauge up, and the operator has to ask permission to gain access to it. The net result is the gauge does not get used, or used properly.What does this mean to the average glass shop? Either too much cerium is used, (which means the cerium is basically wasted, and cerium is expensive!), or not enough cerium is used, which usually means poor quality bevels.
The Common Salt Water HydrometerHere’s another solution!It is also possible to use a common salt water hydrometer; available in any Hobby Aquarium store that carries salt-water fish supplies. I bought one for under $7.00 USD recently. A salt-water hydrometer is not calibrated in the same scale as a “baume” gauge.Here are the results of direct comparisons between a commercial baume gauge, and a standard off the shelf salt-water hydrometer:
- A salt-water hydrometer is calibrated (as is a Baume hydrometer) in specific gravity.
- The scale on the salt-water hydrometer runs from 1.000 to 1.060.
- My research has indicated that a good correlation between 3 to 5 on a “baume” scale crosses over to 1.040 to 1.050 on the salt-water hydrometer scale.