That is why I said
sometimes. I have had blades where it completely disappeared during sanding until etched later on in shiage-togi. If other cases I can clearly see the hamon all the time during sanding.
Decarb should all be gone long before 600 grit. If you are still seeing the old decarb line you haven't taken off enough metal.
Hadori polishing is a good way to make a weak hamon show well. Sometimes it is the only way to get the yokote to show as well.
You can even do it on a blade with no hamon to get a faux-hamon effect.
I have developed a hybrid hadori polish I use with good results. Here is how to do it:
1) Sand/polish/finish the blade to the degree you want and do whatever etching you want for the hamon. If the hamon is not very clear or barely shows, do a modified hadori polish. As to how fine a finish you take the blade ... it is up to you.
2) Using a model paint like Testor's or other enamel paint, paint from above the hamon (shinogi-ji) right to the line where you want the hamon effect to show. You don't need to paint the whole upper bevels, just make a 1/4" wide masking line. The shape and position of this masking will create the frosty lower surface to the edge. I usually use blue tape to cover the rest of the upper bevels so I don't have to worry about smudges and scratches on the polished ji. Frog tape is also good.
3) Using a paste of fine grit silicon carbide powder and a few drops of choji oil, fold a makeup removal pad into a triangle and use a small amount of the paste to polish the surface from the edge to the hamon (ha-ji). Be careful because you are doing this right on a very sharp edge.
The grit size you use determines how frosty and contrasting the ha-ji is to the shinogi-ji ... and thus how distinct the hamon transition shows. It can be as coarse as 220 grit or as fine as 1200. 400 is good if the blade bevels have been polished to at least 800-1200. on a mirror polished blade ( not my cup of tea) the hadori can be 1200 grit. Experiment on an old knife blade to see the effect. You can start with a lower grit and work up to a finer grit just like you do in sanding.
4) Once the entire blade has been done and you like the frosted effect, wash the blade well to remove all stray grit. Wash your hands and clean up the area you have been working in. Use acetone to remove the paint and clean the blade well. Go slow at first because there may be some of the SC imbedded in the paint. Oil the blade as normal once clean and dry. You should have a crisp hamon line where the frosty white edge meets the shinier upper area. Resharpen the sword if needed. I have found that using a handheld EDM stone is a great way to touch up an edge that just needs the apex restored.
Here is a very detailed article on traditional shiage-togi done to NBTHK standards. Few knifemakers will ever go to this degree, but the info is very good for polishing techniques and materials as well as how to make different hamon types show.
The sword site I just linked to is a newer site with expert info and articles. They use research by experts, not AI, to write their blog articles. There is a lot of good reading in the many blogs they have posted.
Blogs -
https://swordis.com/blog/
At the bottom of the Blog page is a great basic glossary/dictionary for all types of swords. Click "Sword Terminology", and then click either the category shown or "View All Terminologies". That page will have categorized glossaries specific to many different sword types and subjects.
