Steampunk and the Golden Penny Effect

(Or: “How to Perform an Assault on Batteries”)

[Note: this project was the basis for my article in Steampunk Magazine #4, “Brass Monkeying”. Making brass in the kitchen/workshop was an exciting discovery for me, and I hope you enjoy it as well. Go make something INTERESTING, already].

I was looking at brass stuff and came across the “Golden Penny” lab demo, which is a cool demonstration of making brass happen right before your eyes. Since I was fiddling with some copper fittings and planning some cool goggles, I wondered just how they’d look with a brass finish.

The lab requires a strong potassium hydroxide solution and some zinc. Luckily, alkaline batteries contain enough of both for the penny trick. The diagram below is from a damned good article.

 

 

The easiest way I’ve found to get at an alkaline battery’s zinc & hydroxide stash is to use a “tube cutter”, a tool designed to cut copper tubing. I chose the “BrassCraft Screw Feed Tube Cutter” (#T004), from Home Depot. It will handle tubing (and batteries) from1/8 inch to 1 1/8 inch in diameter, making it just barely able to handle a D-cell battery. (Update: if you regularly deal with electrical installation, a conduit cutter may actually work better, being capable of cutting metal electrical conduit and are available in larger diameters. Just another data point).

You want to cut off the “-” (negative) end of the battery (the end with no ‘nipple’). Position the tube cutter as close to the “-” end of the battery as you can.

 

About 10 seconds after you start cutting, the end will be free (you are wearing gloves for this, right? I didn’t for the first battery, and I got ‘minor’ chemical burns on my thumb).

That silvery ‘toothpaste’ in the middle is what you are after. You can pull the whole lot out of most batteries with a pair of pliers. It’s all wrapped up in a moist paper-like tube. That assembly on the right is the bottom of the battery with the brass current collector “spike” sticking up. No carbon rods here, babe, were cooking with alkali!

 

The tube can be unrolled and the zinc paste scraped off or squeezed out of the end like toothpaste.

Put the the paste and a tablespoon of water into a cookable non-aluminum container (a Pyrex© lab beaker would be ideal, but I used an old tin lid that I could just throw away afterwards). Place several old (pre-1982) pennies that have been degreased (with scrubbing, abrasive cleanser, detergent, a hot water rinse, lightly etched in muriatic acid followed by another hot water rinse), into the goo and turn them, smooshing them so that they are coated well (I used an old stainless steel fork for this).

Put the cookable container on the stove and heat it to boiling, replacing the water as it boils away (wait until it gets thick like oatmeal, don’t add too much water since you don’t want to over dilute it). Good results can obtained with less than 3 minutes of total boiling time (longer boiling time = thicker zinc coat = brassier brass).

Remove the container from the stove and let it cool, then fish the pennies out of the caustic zinc goo (I used the fork again). The pennies will have a nice chemically applied zinc plating (see center penny below), looking very silvery. Now, wash them gently but thoroughly in water, being careful to not disturb the zinc plating.

Heat the zinc-coated pennies over the stove burner (I used an alligator clip stuck on a fork tine to hold them over the flames one at a time), turning constantly to heat them as evenly as possible. Watch carefully! In just a few seconds, the pennies will turn a lovely golden brass color. Immediately quench them in water. If you cook them too long the brass color fades as the zinc “migrates” deeper into the copper or vaporizes into into the air [sorry, no pictures of the final “flaming” at this time, too busy minding the fire].

 

Scaling Up

The above brass conversion process can be easily scaled up to handle larger copper pieces. Donning protective gloves, goggles and apron first:

1. Fill a pyrex cup or bowl 3/4 full with boiling water water, [edit 2008/4/16] add 1-2 tablespoons of sodium hydroxide (available in most grocery and hardware stores as “household lye” for cleaning drains) per cup and some zinc (extracted from batteries or purchased at a marine supplier or stained glass studio).
2. Lower the cleaned & etched etched copper pieces into the hot plating solution, after a few minutes they will be covered in a beautiful layer of zinc plating.
3. Even heating will cause the zinc to combine with the copper below, resulting in brass. If you have applied the zinc with a patterned resist, a patterned brass design is obtained.

UPDATE 2008/4/16: See the “Etching Copper…” post for information on applying a mask with the toner transfer method. Been there, done it, works great. You might wanna do some pre-zincating touch-up to guard against pinholes in the toner (at least if you use a Brother HL-2000 series printer, which is, overall, a great printer).

Tags: brass, cheap, cool, copper, DIY, fun science, zinc