You can buy Logwood Trap Dye online from Dartmoor Sheepskins in the UK.

Logwood chemically converts rust (iron oxide) into a more stable compound (ferric tannate).

The tannic acid in the ground logwood bark can convert any surface rust it comes into contact with, but it won’t ‘soak in’.Start your rust conversion by removing any unsound surface material – so the logwood trap dye can reach all the rust to be converted. 

What is Logwood Trap Dye and how do you use it?

In its simplest form logwood trap dye is the ground up bark of the logwood tree, added to a bath of hot or cold water. The tannic acid in the logwood dye reacts with the rust (iron oxide), changing it into a different and more stable compound – ferric tannate.

Rust-covered metal can be ‘painted’ with the watery rust converter, or can be placed in the bath for a good long soak. The hotter it is, the shorter the rust conversion time – use an open fire or even add freshly boiled water to speed things up.

very close shot of the hammered end of an old splitting wedge.

While even a luke-warm bath will have done its work in half an hour, a completely cold solution should be painted on and repainted if it dries too quickly.

Often the manufacturers will have added polymers which thicken the watery solution – we don’t. Instead we use agar, which thickens in time – this slows evaporation and aids adhesion, particularly useful when painting above your head.  

a spade head and wedge ready for rust conversion

Dartmoor Sheepskin’s logwood trap dye is made from pure logwood.

The only addition necessary is the option to add agar which results in a rust converter solution that closely resembles jelly after a few hours – it doesn’t reach this stage quickly, rather as time goes on the trap dye sticks with a progressively more jelly-like viscosity.

Without any artificial polymers, our logwood trap dye is thin enough to reach everywhere, and then the agar thickens up, staying where it’s needed for long enough to see the reaction through. 

Even by using boiling water from a kettle to mix with the powder one can reduce reaction times down to just a few minutes. For use in hot dry locations, select Logwood with Agar as this increases evaporation time.

The same applies when rust treating hard-to-reach metal and undersides. Where normal trap dye would otherwise drip away or evaporate, the agar has the staying power, naturally.

What is logwood trap dye?

Logwood Trap Dye is logwood that has been shredded or powdered in order to mix with water. The dye that is produced contains such high quantities of tannic acid that all iron oxide it comes into contact with is chemically changed into more stable ferric tannate.

Most commercially available logwood trap dye will have polymers added to aid absorption. Dartmoor Sheepskins Logwood Trap Dye consists of all natural ingredients – you can choose to have logwood and agar, which thickens the trap dye allowing it to be painted in awkward places. This gives the trap dye longer to do its work, and the rust converting jelly is easily washed off the next day or so. 

It’s easy to imagine the dye is not going to work because it goes on like water when it’s fresh (even with the addition of agar), but it delivers the tannic acid and the only other thing needed is a little time. In very cold regions an unheated trap dye bath should be left for longer, but it’s literally the case that you need do nothing but wait – the metal can be inspected at any time to see if it’s ready. 

Why do trappers use logwood trap dye?

The American trappers developed the technique of ‘dyeing’ their traps prior to the season’s first use. They weren’t the first people to use tree bark to stabilise rust – evidence of oak-based rust conversion can be found all over the world. But the logwood not only supplied tannic acid by the bath load, it also does two other things: 

  1. It has a strong smell, that won’t alarm animals. Even if the dye bath is heated over an open fire, the human smell is totally obliterated. 
  2. The treated metal is black. Reflections are reduced dramatically as any and all rust is converted by the logwood trap dye.

Fortunately, trapping animals is banned in many places, including here in the UK. However, some useful techniques can be learned from trappers, who want some of the same things that the rest of us do.  

Chris DS
Logwood trap dye has converted the rust into ferric tannate