Another great learning experience. Thanks again Dennis!

Tannic acid should be reacting with iron oxides to form ferric tannate which is a blue/black pigment.  Historically ink was made by dissolving iron in a weak acid like vinegar and then adding tannins extracted from oak galls.  You might try a longer etch to have a deeper oxide layer for the tannic acid to react to.  Also you might look into rust converter.  It is made to turn red iron oxide on tools and  equipment into a black finish and coincidentally most rust converters have tannic acid as their active ingredient.

Cool experience!

I'm late to the party but I had bought some tannic acid for a wood treatment project I'm working on.  And I bought that exact tannic acid you used on here.   If you decide to try this again you should just use distilled water and the tannic acid by itself and then fully submerge the metal.  It will take a minute but eventually it will go from Rust to ferrous tannate to ferric tannate on the surface of the metal.  I was about to try this on some of my equipment that's already rusted, since I already have the tannic acid.  Ferric tannate suppose to be a good protectant for metal.    Thanks for creating this video.  I enjoyed it.

☕️ good morning 😊

@tyrellknifeworks you should try etching in ferric first and allow the steel to sit out and start forming red/brown oxides for a bit.  Then submerge in the tannic solution

In the Royal institute they preserve iron relics with Tannic acid and Phosphoric acid; 2% to 5% Tannic , Deionized water  (very important for eliminating Chlorine ions) and Phosphoric acid to bring the pH to at least 2.4 or slightly lower (more acidic) but not too acidic :)

Yup i will stick ferric and coffee if necessary. It is by far the cheapest with the best results. There is an ABS mastersmith that only uses ferric and does things a little different and gets great results whose method i will also try when i run out of instant coffee.
I enjoy seeing folks give it a go with other stuff such as the tannic acid, other acids and the idiotically named "gator piss"....but nothing beats the originals.
Thanks for posting

I love science! The steel being darker on the bottom side, might be because of stronger sediments on the bottom of the beaker, meaning that it probably needs to be constantly agitated, during the process? 🤔 I think it's awesome to try different methods, and materials, to achieve better results! Can't wait to see how this comes out! Thanks for sharing my brother! 💯😎👍🏻🔨🔥🔪

If you had add FeCl3 to the tannic acid solutiion you would have gotten an adhesive film on all the walls of the beaker and on the steel plate. The film is tannic acid and its strong enough for masking puposes before etching.

my only issues is finding tannic acid powder online. why is it so hard to find.

Where is part 2

I use CLR (the brand, calcium lime rust remover) it takes a while, but the etch is easier to control and gets decently dark.

Disclaimer - scientist here😉
When performing experiments that are supposed to optimise some procedure, I always! include a control sample so I have a direct comparison at the end to avoid these "inconclusive" results. I understand that you know how it's supposed to look after coffee etch but still.... In any case, I love the scientific approach. Most people just stick to the old protocols, don't ask questions while the methods should naturally and constantly evolve👍👨‍🔬

I would love to see this side by side with coffee and a solution that's just the dilute HCl

Coffee seems easier, it should be a fairly valid etchant though like most acids, some of the darkest results I've gotten on just low/no alloy carbon steels is with boiling vinegar which is quite quick (just don't do it inside or anywhere outside near steel because the vapours are going to rust everything!) and Nitric Acid. I'm not a fan of nitric though because its difficult to get (because it makes things which can be explosive) and it is liquid hell for anything or more particular, anyone it touches.
Maybe do a side by side of a sample metal, same material, heat treat, cut it in half and then do the etch, then a darkening cycle in tannic with another in coffee sludge

Wait.  You're telling me that smiths are enchanting their weapons now!!?  I've wanted a +5 enchanted longsword since I was 7.

I love your videos, can I get a comment heart?

now it's clear why we use cofee: cheaper, easier to obtain, easier to mix, non toxic, faster, more effective..

Was the test piece you used just 80crv2 or damascus made with 80crv2? Not sure you'd get a meaningful result with monosteel in your test solution. Either way, thanks for being curious enough to test something most of us haven't used (or heard of!). Based on your preliminary results, cheap instant coffee seems less fiddly and safer, but I'm no chemist.