Perilous Purple Coffer

July 2005

Front view of the coffer

A coffer of mahogany, made as a birthday gift.


front three-quarter view, showing lid and hinges

I don't normally use tropical timber, but this was made from some short offcuts from outdoor decking and they were cluttering up my shed. The species is some random African mahogany-like, probably just Brownwood kurtzii

The lid is coopered - made of separate strips (staves) joined onto the frame by bamboo pegs. Rather than finishing them smooth as I usually do, I chamfered the edge of each stave to make a groove between them. I also spaced each strip apart with narrow strips of ebonised oak.


Rear corner, showing the dovetailed joinery and hinge

Dovetailed joinery

Joinery on the corners is simple dovetailing, hand-cut of course.


The box open, showing the clenched nails attaching the hinges

Box, open

The hinges are attached by nails, clenched over on the inside. Each nail is rose-headed by hand, which I'm now really well-practised at doing quickly!


Forged steel rotating hook latch, in closed position

Latch, closed

After a few false starts, I came up with an idea for a latch that worked and was within my meagre smithing talents. I'm still looking for good ideas on new latches and locks.


Forged steel rotating hook latch, opened

Latch, open

It's just a simple rotating hook latch. It's attached through my usual diamond-shaped latch plate. This is riveted in place with more nails and a similar plate on the inside. The corners are bent down too, which locks the plate in position nicely.


Rear view, showing iron swallowtail hinges

The hinges have a forked "swallowtail" shape to their ends. I like these on a box this size and will probably use them again.


Construction

Materials: African mahogany, ebonised oak, forged steel hardware.
Finish is oil and wax.

Overall size, approx 14" x 10"

The ebonised oak process was interesting. I used logwood, generally thought of as a red pigment. Logwood is prone to oxidation and fading to a bilious yellow. To avoid this in the past I've used ammonia as a mordant. Logwood is also pH sensitive, having different colours (red / blue) when exposed to acids or alkalis. In the past I've successfully dyed oak a persistent blue, but have found it difficult to reproduce reliably. This time I was aiming for a deep purple. It was certainly purple when fresh, but it's aging to a darker near-black. More experiments, I think!