The Black Line

The Royal Collection describes Leonardo’s ink as made “by mixing iron salts with tannic acid from oak galls (oak apples) to give a thick black ink”: iron-gall ink.

On Leonardo’s pages, the Royal Collection says, it has mellowed over the centuries to a warm chestnut.

Cabinetmakers learned to imitate it on cheaper woods, and the result is called ebonised.

The V&A has a Dutch linen press of 1630–50, oak with “applied motifs in ebonised wood”, and an Antwerp table cabinet of 1640–60 that sets real ebony beside ebonised wood on an oak carcase.

The first was ebonised deal, a cheap wood. When the deal proved unstable he changed to ebonised mahogany, and at least ten were made over the next twenty years.

The V&A says it “epitomises the influence of Japanese art and design on British decorative art in the 1860s and 1870s.”

They made it in large quantities, and William and Jane Morris had Sussex chairs at Red House and at Kelmscott House.

Black country chairs were nothing new. In north-west England in the early 1800s, customers could have their chair frames stained black, or stained to look like mahogany.

Ours is the same pairing: iron and oak.

The jigsaw joints never felt right, so one of Harley’s first jobs as our apprentice was to find another way for the pieces to join. He came back with arrows.

The engraving was beautiful up close and vanished across a room, and we didn’t want paint or dye on a child’s toy. So we went looking for how wood was blackened before paint came in tins, and found a recipe that sounded made up: put iron in vinegar, wipe it on oak.

We don’t work with metal, and we don’t clean much either. The vinegar came from home, from the five-gallon jug that lives in the cupboard (bought in bulk from Amazon, where we’re happy to shop, even if you won’t find us selling there), carried back to the workshop in a jar. The steel wool came back from the shops as stainless steel scouring pads, which sat in the vinegar for a week and did precisely nothing.

So Harley suggested we try Andrew, who runs Blackford Engineering across the yard. We found him working on one of his classic cars (he films them on his YouTube channel, The Vintage Workshop) and walked in holding a jar of clear liquid. Stainless pads are treated, he told us; they’ll never do anything. He found us some real wire wool, oily, about a teaspoonful, handed over with the air of a man who wasn’t giving away any more.

Overnight: nothing. A week: still clear vinegar with some wire in it. We decided it didn’t work and left it on the shelf. (We know now that iron dissolving in vinegar gives off hydrogen, so a tight lid wasn’t our best idea.)

About a fortnight later, more out of stubbornness than hope, we brushed the sludge from the bottom of the jar onto a practice tile: a dragon from last year’s puzzle. It went jet black. Not just the lines, the whole tile.

It’s why every tile is now sealed with shellac first, so the iron can only reach the engraved lines. Our shellac comes from Wrights of Lymm, who also make our gold leaf, and who hold the Royal Warrant as suppliers of gold leaf and gilding products to the Royal Household.

The gold came next. Iron needs the oak’s tannin to turn black. Purpleheart and padauk have barely any, and they’re too dark to show a black line anyway. So their paths are laid in 24ct gold leaf instead, and they became the magic tiles: the wild card that joins any path, wherever the story needs it.

The first time we made these, they didn’t go to plan either. We used 20-hour size (the adhesive that holds the gold down; food safe, for the record). Little did we know that ‘20-hour’ meant size that takes twenty hours to turn tacky. No wonder our gold didn’t stick, and you can imagine our disappointment until we realised the mistake.

There’s one more wood in the corner of the workshop: a small stock of Osage orange, hard to find in the UK. It has enough tannin to take the black line, but gold would vanish against it. There’s only enough for about twenty tiles, so we won’t make them until we’ve found the right design.