Glass Stirring Rods and Spatulas

[UC]

Glass stirring rods may not be anywhere near the most expensive equipment the average amateur chemist owns, but they are nonetheless ubiquitous. I also think it's nice to have at least one piece of equipment that you made in some way.

 

Current ebay prices put the typical 6mm wide, 12 inch (305mm) long stirring rod between $0.75 and $1 (USD) each before shipping. Instead of spending my money on a dozen or so stirring rods, I purchased a large quantity of 6mm diameter clear borosilicate rod for glass working. I won 5lbs of rods for only $5 (which comes to 51 pieces that are 24 inches (610mm) long) and picked them up since the seller was fairly local. Stirring rods that I make from this glass cost me slightly under $0.05 each. They look like this as obtained, with crude broken ends:

 

 

Normally, glass working (especially of borosilicate) is done with high-temperature torches, but for the simple application of rounding the end of the rods, a plain propane plumbing torch is sufficient. To round the ends, hold the rod vertically in the flame like this:

 

 

The glass does not soften too fast with such a cool flame, but after a minute or so, it has liquefied enough to ball up. After cooling, it looks like this:

 

 

Repeat on the other end of the rod. Of course, these rods are 24 inches long, which would make for a very inconvenient stirring rod. Half of this length is, however, a very nice size. Locate the center of the cooled rod and make a mark. You could just use brute force to break the rod, but if you have a fine metal file, you can do better. Place the rod against a hard surface and slowly "saw" with the edge of the file perpendicular to the glass rod until you make a small notch in the glass like this:

 

 

Slowly rotate the rod while continuing to "saw," using the notch as a guide until you make it all the way around. It will look like this when you finish:

 

 

I recommend wrapping a towel around the rod before you break it to prevent any glass chips from going flying. Apply a moderate amount of force to the spot where you scored the glass and it will give way with a more or less clean break. Mine, shown here, didn't want to cooperate with a perfect, flat break, but you can see that the break propagated mostly. along the scored line:

 

 

Repeat the procedure with the torch to round off the new ends. Repeat and you have yourself a lifetime supply of stirring rods for pennies.

 

Making a glass spatula

 

The typical laboratory spatula is stainless steel, which is acceptable for most commonly encountered chemicals, but fails for things like copper (II) chloride or iodine when even traces of moisture are present. Plastic spatulas are also available, but for 5 cents, It's easy enough to make one out of glass.

 

For this, you'll need a pair of cheap pliers without teeth, which have a reasonably large surface area to the jaws. I use a pair of 8" linesman's pliers that I took a shop grinder to. Heat up the end inch or so of glass until it starts to get soft, then insert the pliers into the flame (hence the need for cheap, as this will ruin the temper) and use them to flatten the glass, reheating between each squeeze. When working with such a low temperature flame, removing the glass item causes it to harden almost immediately. The metal on the pliers is a conductor of heat, and thus a bad choice for glass working, but still usable if you take care to reheat the piece often. Use the jaws to reshape the spatula as you please and put a bend in the end of it like this:

 

 

I wouldn't call them pretty, but they will do their job with the more aggressive solids in your chemical library. The small amount of rust on the right spatula was from the pliers and is embedded in the glass, where it can do no harm.