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Cold Cure Japanning
Until around the end of WWII at least, Stanley iron planes, along with most of their competitors “painted” their plane bodies in a black tar-like lacquer. This is a very durable finish. However it does wear, generally as a result of planes rusting over many decades, and lifting the japanning.
Restorers seek a way of returning their hand planes to original condition. Some strip the old, mangled japanning and spray the bodies with car enamel, engine enamel, and rust proofing (such as Rustoleum). It never looks correct – too smooth, clean, and too modern. Old japanning was never perfect. It was grainy and a little lumpy.
The heart of japanning is asphaltum, which in powder form looks like dark brown soot. The traditional method is to bake this on to the iron, which is smelly, and may create noxious vapours. Do not try it in your kitchen oven!
I received this cold cure japanning recipe of Stephen Shepherd – quite simply, it is half asphaltum and half marine varnish.
Stephan has been doing this in the USA, and his ingredients are a little non-standard …
"I use roofing tar, but first let the volitiles evaporate, then mix it up with the McCloskey's Marine Spar Varnish (Gloss)”. I put the stuff on both wood and metal and it seems to be very durable. It is important to prepare the surfaces, I use alcohol on metal to clean the surface of any grease or oil. I may wash them with soap and water first, surface prep is important. As far as baking the stuff, I of course don't bake the wood, but I will set the piece in direct sunlight, it helps cure the finish. On metal I do occasionally bake it but not at a very high temperature, 220 degrees F. I have done this for Ferro-type or tintype plates for a friend that does historic photography. If you don't bake it is a bit soft for a while but in a few weeks it hardens up. I am sure Stanley and the other makers of metal planes used Japan Driers in their recipes, which I believe mine is close. As for the look, it is spot on, deep black with tinges of brown showing through on edges, this is the real look, which can not be achieved with any kind of modern paint or powder coating. It also works well for inpainting missing japanning on metal objects. I restore a lot of tin ware, which is where my experience is, as I do not own any modern metal planes."
Stephen confirmed: “Here in the US roofing tar is asphaltum. Asphaltum is available from a variety of sources and can be spendy, roofing tar is cheap, I have actually never bought any as when you tell someone that is tarring a roof, they will usually give you some.”
Stephen wrote me after this was completed: “Depending on temperature and humidity, the spar varnish will dry in 8 to 24 hours and will continue to cure for a few weeks. The asphaltum element adds some time to the drying process and hardens up as it cures. It will take more time, but you get the right look by using the right materials.”
It was exactly what I was looking for. Having used it now, I can confirm it looks the Real McCoy. One word of advice - it is self levelling if used on a flat surface. If may leave runs if used on a vertical surface. So do one surface at a time.
asphaltum (powder from an art supply store) with marine varnish until
it is thick like treacle. Paint this on in thin coats. Build the
coats up as they dry or become tacky.
The colour will start off as a muddy brown-black, then become increasingly darker, and eventually black.
It can take about two weeks to dry without heat, but you can speed up the process by heating to about 220 C or leaving it out in the sun.
This is both authentic looking and durable (unlike paint).
Regards from Perth