Acid Polish, How can you tell?

[Munechika]

Greetings folks,

 

I have been wondering how can you tell acid polish from traditional polish? Would anyone want to elaborate on this subject?

 

From what i understand and read online, acid polish do not bring out the true activity of the hamon and furthermore weaken and damaging to the blade.

 

Is a sign of an acid polish too flashy and often shines the hamon? Not only that, does it not have a natural flow of the grain in the ji connects to the hamon in the temper edge? Is the hamon is just too shiny, the blade shines, grain not clearly visible and activity like sunagashi, kinsuji, and nie-deki (if it has it), is masked by the mirror reflection of the acid polish?

 

Attached is a picture of Ko-Ichimonji Sanetoshi that i download from web (i think it's from Ginza Choshuya Website awhile back) that i use to study. From the polish of this sword, the grain glitters with ji-nie. Chikei (i think) are clearly visible; utsuri appears, and the hamon are so well done that abundant of kinsuji, sunagashi and patches of what i believed to be ko-nie naturally melted, solifified, and settle-down in hamon from the ji, lighten up the blade. If the sword has these type of characteristics, it would show up on the traditional polish and not on the acid one am i right?

 

God I love that blade!

 

From a newbie newbie,

Nhan Nguyen

[Mike P.]

I believe that would be a traditionally polished blade, in this case the hamon has been beautifully enhanced with a hadory stone.

 

An acid etching can take many forms and even be especially deceptive in photographs, and I don't think that any written guidelines could give you a sure way of looking at a photograph and deciding one way or the other. Seeing the blade in your hands would make it easier do tell the difference, however only the experience having seen many traditionally polished blades can give you an accurate sense of what you are looking at.

 

As you know the blend of steels of different properties on the surface of the blade will react differently to the acid and create relief micro patterns, for a much coarser velvet than would be achieved with fingerstones. Sometimes this can only bee seen when the blade is in your hands. Sometimes the etching has been prolonged and the surface will have a more damaged appearance, like damascus. A white hadori-type hamon that precisely follows the habuchi might also be a sign of chemical enhancement. But sometimes it has been performed in an skilled deceitful manner and might be extremely hard to see in a photo, or even if the blade is in front of you, as not all blades have structure detail.

 

In this case, you have demonstrated excellent taste on a beautifully performed traditional polish (or is it? )

 

Mike Pilo

[Munechika]

Thanks Mike for some insights :D

 

Nhan Nguyen

[reinhard]

Nhan, traditional polish is not a perfectly uniform procedure. Polishing techniques changed slightly during history and polishers started etching blades during late Edo and Meiji-period. From what I have seen in museums, etching in the later 19th century was a superficial finish only and did not create any relief pattern. Nie-based features like chikei, kinsuji, sunagashi and the like appear extremely flashy at the expense of nioi-guchi. However, I have never come across a top-quality blade (Ichimonji f.e.) "improved" by etching. All examples I have seen up to now are either mid- to low-quality blades from bakumatsu-era or crude gimei. Etching gained some popularity again recently, but is mainly applied to ShinSakuTo, if at all.

Here's an example of a (hozon token) katana by MICHITOSHI from Edo, dated Bunkyu 3rd year (1863). It has been slightly etched.

 

reinhard

[Munechika]

Thanks reinhard for a lovely picture and history as well as insight on the matter. So acid polish or acid etched is rooted around Edo period. Though I must say differenciating which is acid polish and which isn't is difficult to say the least. Based on the picture you provided, acid enhanced is the last thing come to my mind until you said it was. Who would have guess (well beside a professional polisher lol).

 

I guess like Mike said, holding an sword in and evaluate (probably go with the gut instinct). And instinct arise from years of experience.

 

The reason I asked such question simply because acid polish tend to weaken the steel of the blade. It might be a useful insight to know which is acid enhance blade for any important future purchases.

 

Looks like i have lot of searching and reading to do in my spare-time. (Knowing which stones is used on which step resulting in what... might shines some light on the matter)

 

I cant wait until I take Physical Chemistry. Maybe then I'll know why acid weaken the blade (beside microscopic rust and attacking the crystalline structure of the steel...)

 

Again thanks.

Nhan

[Tavroch]

Example of acid etching?:

https://www.aoi-art.com/auction/en/auction.cgi?acc=disp&no=1239159584&t=1213703271