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Advice needed for keeping a high contrast when finishing a San Mai blade


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Hello everyone,

 

I've viewed many topics on this forum and this is my first post. I'm looking for the advice of bladesmiths more accomplished and knowledgeable than I am as a hobbyist at best. I've been making knives for about 4 years and I've recently gotten more serious into pattern welding. I've checked out countless forum threads and youtube videos and can't quite find what I'm missing, which is the very end of the process where the high constant finish is locked in on the finished blade.

 

I'm very familiar with the underlying etching process in both ferric chloride and coffee and I've done a few blades previously that were of low contrast. I've read that San Mai's are also allegedly a little more difficult due to the lack of valleys and ridges on a portion of the blade during the etching process, but for the life of me I can't get the oxides to stick to the blade enough to keep the contrast high. 

 

For example:

 

This is a test blade that I've been experimenting with. It's 1095 and 15N20. it's been hardened and hand sanded to 400 grit, lightly buffed, and cleaned with rubbing alcohol prior to any etching. it's free of any weld spots, grease, soap etc. I do my initial etching in a 1:3 ratio of diluted ferric chloride for 15 minute soaks (with gentle cleaning in between) until I can feel the elevated 15N20 with a fingernail. Then I neutralize in baking soda/water and move to freshly brewed strong coffee at about 120 degrees and soak for 4- 6 hours before the 15N20 starts to stain brown.

 

Then I remove it and let it air cool for a few hours (or pat dry with the same result) and go to remove any remaining loose oxide. This is the part that is driving me bonkers. The pic on the left if how it looks fresh out of the coffee which is stunning. Then after washing the blade with soap and my fingers alone, then lightly passing with either a soft cloth or 0000 steel wool I get the less than stunning pic on the right and a ton of loose oxide coming off the exposed 1095 areas the blade leaving it only grey and cloudy.

 

I've also tried boiling the knife for 30 minutes to solidify the oxides with no change. 

 

So am I missing a super secret critical step somewhere in the process or are my contrast goals perhaps a bit too unrealistic?

 

I see many bladesmith produce pictures of stunning contrast and I can't imaging that it's due to leaving fragile loose oxides on the blade of a knife that would come off so easily. I've heard that 1075/1084 will etch darker in coffee, but 1095 is what I have the most of. I'm also trying to keep the finish food safe without any bluing or clear coats.

 

I appreciate any and all responses and please forgive me if I sound frustrated as I'm all out of tricks on this one:-)

 

Justin

 

 

 

 

 

IMG_20210423_192702.jpg

Edited by Justin Byrd
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Looks like you're cleaning it too vigorously after the coffee etch, and maybe letting too thick an oxide layer build up.  I personally haven't done the coffee thing, but I wonder if using it hot is not the thing to do?  At any rate, you can always hit it with instant cold gun blue/black and wipe, don't sand/wool, it off the high spots.

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Justin, welcome and that’s a beautiful blade. 

I am commenting because etching too often leaves me frustrated. Last San Mai with wrought over W2 I did, went through at least 12 etchings and still not please so I sanded off, went to 2000 grit and stopped.

Everything Alan said are top recommendations to follow and investigate for sure. 

I might add that after coffee etch, I’ve had better results boiling the blade in distilled water (at least 10 mins), as I believe it sets the oxides. There still be some loss in contrast but not as much. Also I realized there isn’t as large a variance in the high/low topography, as I thought.... so after the etch......I am sanding high and lows! I need to improve my pre-etch prep getting the blade ready to etch.

 

Gary LT

 

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Thanks for the replies and advice Alan and Gary.

 

I did try a 3rd brand (McCafe coffee) and oddly enough it behaved exactly as I expected it to. I ended up doing a  3 hour cold soak (I must have read your mind Alan) and when it was done I just patted it dry and then went to some light cleaning and hardly any oxide came off and very little cleaning was needed and the oxides are locked in. I could have probably gotten it a little darker, but I was more than happy after 3 hours.

 

Gary, I feel you man. I always look at my etches and think they can be better. My full patterns turn out better than the san mais I've tried, but this may change it for me. 

 

Again I appreciate the help!

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6 minutes ago, Alex Middleton said:

Very nice!  Thanks for taking the time to post.

Anytime, thanks for the compliment and for checking it out! It's cool here and I dig it.

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Looks nice. A steel with more Mn in it will go darker (try O1, but its not an easy steel for pattern welding) 

 

One thing I found to get great contrast is to make your shiny high layers shinier (rather than your dark, darker)! - Try hitting it with some 2000g wet and dry paper, on a hard, flat backing. If you get a smidge of topography from the etch its possible not to 'scuff' the dark layers. It will really pop.

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oh, and in my experience, don't buff the blade before etching, it 'smears' the mountain peaks and valleys that the acid bites on. Muddies the whole thing up. I get good etches from 400 grit. I have found if I go to a finer grit the etch is worse. 

 

Pondering, on a micro scale, could the 'dark' we see with our eyes be 'in the valleys' of the grit scratch profile?! - discuss.........

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Thanks, John!  I totally missed the buffing/steel wool thing.  Yes. Do not buff, ever. Do not use flexible or loose abrasives after etching. Hard backing all the way. And good idea about micro-topography and darkness.  Maybe?

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