How to get a black, shiny finish on forged items.
By Bjorn Jacobsen, 20th of Nov 2020.
Many times when forging bottle openers, hooks and other little gadgets I have wished for a better looking finish than the scaled, mottled apparence straight from the forge.
A little while ago a recipe was posted on a blackmithing group on Facebook about "pickling" forged items in citric acid and this is our results with this recipe plus some help from Mareko Maumasi.
The challenge: Get a nicer finish by removing some or all of the forge scale without having to try grinding it off.
The solution: Citric acid bath + scrubbing + Torch blue + wax
What we started with; a forged dragon (sick cow?) head that was wire brushed a bit after the last heat but otherwise not finished. It is a dull, mottled finish.
We ordered some Citric Acid online, this comes as granules and we mixed about half a kg into a 10 liter bucket of water, creating a mild acidic solution. Citric acid is used in lots of food products and is low-cost and easily available. (hmm, remind us to try etching damascus in this as well at some point)
Then we popped the mutant cow dragon thingie into the citric acid and water bath, leaving it for 24 hours.
After a day in the citric acid bath we fished it out and rinsed it well under a running tap. The original recipe called for a baking soda bath but we assume the acid is washed away and neutralised just as well by a running tap.
We then scrubbed it fairly well with a rough kitchen sponge and most of the black forge scale seems to have been eaten away. What is left is a dull, grey finish.... different but not all that nice?
Here is the back of it next to another one we did to show the difference with and without citric acid bath (the left, grey one is the one that was pickled in citric acid and then brushed with a rough kitchen sponge)
It is cleaner and now the corners would be very easy to highlight further with a scoth brite belt, soft wirebrush or similar. But it was not super nice still, more just dull grey.
Then we saw Mareko from MaumasiFireArts (Instagram link: HERE) showing an awesome looking bottle opener with a much darker, richer finish:
A couple of messages later we learned that Mareko torch blues the steel and then add wax while still hot.
So we combined the recipes (or just copied Mareko?) into this:
- wire brushed after forging, from red hot
- into citric acid bath while still hot to "quench pop" off a lot of the scale, then leave it in for an hour
- neutralise the acid under a running tap while scrubbing with a kitchen scourer
- flame darken using a MAPP gas torch (we left the bottom hook part alone to show the difference this makes)
- add forging wax from ValdyrJarl (Intagram link: HERE ) while still hot from the gas torch
Result? A clean, black finish with hints of blue/purple tempering colours here and there and an even, shiny waxed finish! We love it and have started doing this on bottle openers and other small items now.
In the last photo it is clear how much of the scale comes off from the citric acid bath or "pickling" after only 1 hour in the bath, check out how clean the hook or tail is. Perhaps we made it way too strong compared to the original recipe by mixing 500 grams of citric acid granules in 10 litres of water (?) but this seems to work well in just one hour.
Then it is clear how much the flame darketing adds by creating an even, black finish that the wax locks in, preventing it from rusting. The forging finish wax from beeswax and terpentine smells amazing, we applied it by placing the hook on a cotton rag and holding a small lighter flame inside the wax can until melted wax dripped over the hook that was still warm. We then rubbed the wax in with the rag for a rich, dark finish.
Final note: The next weekend we did another version of this by citric acid bath "quench" and leaving it in there for an hour. Then rinse and scrub and then clean up highlights on a scotch brite belt before flame tempering. This left tempering colours on the highlights polished shiny from the scotch brite belt and also looked very cool.