Etching Aluminum with Ferric Chloride

I like aluminum as an inexpensive alternative to sterling silver in my Cold Connections pieces,  but have been disappointed in its utility - I already discovered that it won't take liver of sulfur (LOS), after I had textured a piece of aluminum with one of my texture hammers, and wanted to emphasize the texture with LOS:

Aluminum Sari Ribbon Corset Cuff

The circle in the pic above shows the texture I created with my texture hammer: when I ran this piece of aluminum through the LOS, the LOS just pooled and ran off the aluminum like water off a duck's back. Very disappointing!

But I still love the cuff - and it's available on Etsy!

I forgot all about this LOS-aluminum incompatibility when I tried stamping an aluminum piece -

stamped aluminum

After stamping this piece of aluminum, I placed it in the LOS, having forgotten my previous experience. Needless to say, the same thing happened. Without the LOS, the stamping was hardly visible at all - I used another method to darken the stamped impression of each letter, and then sealed the patina with Krylon.

So - I can't really texture the aluminum with hammers, nor stamp it.

Now, I admit I hadn't thought this through all the way, but I decided to see if I could etch a design in the aluminum with ferric chloride.

I cut out 2 heart shapes, sanded, filed, and cleaned them, and then stamped a heart design on each with Staz-On.

Then I placed the hearts in the ferric chloride bath.

When I etch copper in ferric chloride, I leave in it for 90 minutes. So, I turned around, and grabbed an egg timer from the shelf to set for 90 minutes, because I have a habit of forgetting things (I get distracted by other bright shiny objects!).

Thank goodness I didn't leave the room! No sooner had I turned around (my hand wasn't even on the egg timer yet) when I heard an out-of-place fizzing, like someone had poured a glass of champagne, and was holding it up to my ear.

Hmmm ... I thought.

And I turned around; all the while the fizzing was getting louder.

I looked at the ferric chloride, and it was bubbling and frothing like a rabid dog. This is NOT what happens when I etch copper - it just lies there, soaking in its brown acid bath.

I figured I better take the aluminum out of there, since something was clearly wrong - and my hands were a good 2 feet away, if not more, when I became aware of the heat coming from the acid container. And it just got hotter and more fizzy as I got closer. I grabbed the pieces of packing tape that supported the aluminum in the acid (these edges were well-away from the fizzing action, so I wasn't worried about burning myself) but there was tremendous heat coming from that acid container!

As soon as I had raised the pieces above the level of the acid, the fizzing stopped and the temperature returned to normal.

Those of you with chemistry backgrounds say it with me: That was an EXOTHERMIC reaction.

Wow.

And here are the 2 pieces that were in there: (they were black, black, BLACK)when they came out, but after a LOT of scrubbing with steel wool, this is what they look like:

etched aluminum hearts

There is a bit of design; more on the left than on the right. And what you see here is not very deep - you can feel it, but not very well. And that grayish-brown stain in the middle of both of them? Won't come off.

And now that I've thought it through, these designs would have needed LOS to really show, anyway - so maybe not being able to etch aluminum isn't something I need to mourn.

I've heard that aluminum takes alcohol inks really well - so there are still other avenues I can explore with it!