Pressure Flaking Under Water?

Manufacture of stone tools, knives and arrowheads by lithic reduction

Pressure Flaking Under Water?

toxophileken
Registered User
toxophileken
Registered User
Joined: January 15th, 2006, 4:55 am

July 8th, 2018, 11:30 pm #1

Well, thank God we fixed our air conditioning yesterday!  And also thank God we are blessed to have a pool.

Previous to having the AC back, I had been pondering the subject of knapping in the pool.  I've been known to put a weight belt and scuba tank on my chest and lie on the bottom of the pool every now and then over the years, to cool off (did I mention we live in the desert?)...  It occurred to me that there really shouldn't be a (technical) reason one couldn't flintknap under water (obviously percussion would be problematic because of the slowed swing).  Yes, I don't want sharp little flakes on the bottom of my pool.  My wife suggested I sit in a big tub to catch the flakes (she's pretty sweet to humor my weird thoughts)...  And I guess if I ever tried this I'd sweep and vacuum pretty rigorously before the next time the kids used the pool.

Has anybody tried this?

I remember Jim Winn liked to soak some of his rock in water before knapping.  I think he said it helped it flake better, but I'm not sure I remember (or understood) why...  This is sort of taking that idea to the next level...

I envision sitting in the pool, wearing a diving mask and a snorkel, dipping my head in the water to see what I was doing.  Or maybe even setting up a stationary glass viewer (like a glass bottom boat, set up between my face above water and my work under water) to be able to see what I'm doing...

Yes, it's true, people get weirder when it's hot...

Ken
Quote
Like
Share

freeze cracked
Registered User
freeze cracked
Registered User
Joined: October 30th, 2012, 2:24 am

July 9th, 2018, 1:46 am #2

It’s a neat idea. got me thinking.
i dream of a better world in which chickens can cross roads without having their motives questioned.
Quote
Like
Share

Forager
Registered User
Forager
Registered User
Joined: October 22nd, 2010, 11:42 pm

July 9th, 2018, 2:43 am #3

From obsidian flakes and blades Are Tsirk examined microscopic evidence of liquid-induced fracture, and experimented flaking with water, saliva, blood, and honey to verify the characteristic markings associated with liquid media of varied viscosities (even knapping with both pressure and percussion underwater). These experiments suggested that “a significantly smaller force” is required to promote fracture when the stone is wet, a factor pertinent to enhancing control within the variable dynamics of flintknapping (Tsirk 1997).

Detailed passages of his studies and documentation may be found in his 2014 work Fractures in Knapping, pp 112 through 125.  He includes technical discussions of its occurrence and significance, numerous microscopic photos identifying the signatures, and a catalog of these markings identified by appearance and defining mechanism.
Are's Text.JPG
Quote
Like
Share

toxophileken
Registered User
toxophileken
Registered User
Joined: January 15th, 2006, 4:55 am

July 9th, 2018, 4:29 am #4

Wow!  Thanks for the technical answer and the encouragement!

If I made anybody think (other than "What a weirdo"), I'm glad I posted...

Forager, your post refreshed my memory on some of what Jim told me.

Ken
Quote
Like
Share

freeze cracked
Registered User
freeze cracked
Registered User
Joined: October 30th, 2012, 2:24 am

July 9th, 2018, 3:10 pm #5

there have been a number of times when i've worked rock fresh out of the ground and later tried to work same or similar rock that had been out of the ground a while and the difference can be pretty large. some stuff becomes more or less unworkable when it dries out. the problem with rehydrating rock is that it doesn't get saturated very fast, and then when you're hitting it, it's drying out as you're working it so it gets tougher and tougher.

what i am now wondering is if the external pressure of water at depth would provide "support" to the exterior surface of a piece being worked and alter the *location* of the flake run, as opposed to just lengthening the run. i also wonder if the relative incompressibility of water would cause a very short duration delay in the "pooching out" of a flake breaking and allow the ends to stay together enough to transfer energy across the break rather than dying in a hinge.

also kind of wondered if the flakes breaking might cause little cavitation bubbles in the water. 

actually, i wonder a lot of things.  but you knew that...
i dream of a better world in which chickens can cross roads without having their motives questioned.
Quote
Like
Share

Forager
Registered User
Forager
Registered User
Joined: October 22nd, 2010, 11:42 pm

July 9th, 2018, 5:13 pm #6

This sort of wondering made for very interesting discussions with Are, this topic having been among his favored subjects in Fractography.  His presentation of Liquid-Induced Fracture Markings (LIFMs) runs over 17 pages and his catalog of them fills 4 of them, reading something like a field guide for obsidian fracture on a microscopic level. 
Quote
Like
Share

NewbowPA
Registered User
NewbowPA
Registered User
Joined: October 8th, 2009, 5:44 am

July 10th, 2018, 5:25 am #7

Everything I had heard previously regarding 'wet' knapping has been in reference to cherts.    In cherts, wet rock knaps easier than dry rock, which is hardly necessary with obsidian.  As I understand it, obsidian absorbs water very slowly and can be dated by the microscopic hydration layers in the rock which are laid down over centuries.  On the face of it, it wouldn't seem reasonable that water would affect the stone in any meaningful way in a given knapper's lifetime.  Curiosity aroused, I've ordered Are's book (good excuse to have it) to see exactly what he learned and how.  It's about time I started to study flake signatures anyhow.
Quote
Like
Share

Forager
Registered User
Forager
Registered User
Joined: October 22nd, 2010, 11:42 pm

July 10th, 2018, 11:47 am #8

Are had explained that obsidian was the choice of stone for fractography analysis due to its fine composition and readability under great magnification.  He commented in his 1997 Tartu lecture notes that, “… markings, especially the finer ones, depend on grain size. Some markings not seen on a small chert flake may be observed on cliffs of even coarser sandstone, for example.” (Tsirk 1997).  The very finest fracture markings which etch a record of how fracture is propagated - especially the effects of wet fracture - are visible in obsidian.  The practical evidence perceived by many knappers that other stones behave better when wet suggests that the evidence seen in obsidian is present but invisible in flint, chert, quartzite, etc.

His work in identifying and describing the force variables which result in fracture markings serve to explain the mechanics of how fracture is created in stone.  Well beyond his passion for knapping, this had significant practical implications.

In his capacity as a civil engineer, Are formed an independent engineering and consultant firm. Among his efforts in design and research his tasks included:
• Development of methodologies, design and testing of missile silos for blast effects;
• Investigation of failure and distress of structures, including brittle fractures;
• Research on seismic isolation and vibration of structures; and
• Teaching graduate courses on structural analysis and design of structures, including structural dynamics, seismic effects and finite element methods. He held positions as an Associate of Weidlinger Associates, Associate Professor at the New Jersey Institute of Technology, and was the Principle Research Engineer for the Metropolitan Transportation Authority of New York.

It is difficult to imagine anyone else who knew lithic fracture like Are did.  Shortly after his death in 2015 the Journal of Lithic Studies published a brief biography which cites some of his contributions and lists his writings, at journals.ed.ac.uk/lithicstudies/article/view/1293 .
Quote
Like
Share

NewbowPA
Registered User
NewbowPA
Registered User
Joined: October 8th, 2009, 5:44 am

July 10th, 2018, 3:54 pm #9

In rereading, I can see where I might be misunderstood, but my reaction to this thread is surprise, not incredulity.  I had no intention of expressing doubt over either Are's credentials or findings.  It isn't obvious to me how a non-porous substance like glass could be affected by water.  I ordered the book in order to understand why my previous assumptions are incorrect. 
Quote
Like
Share

Forager
Registered User
Forager
Registered User
Joined: October 22nd, 2010, 11:42 pm

July 10th, 2018, 5:50 pm #10

NewbowPA I regret that my response to your comment may have been misconstrued.  Your sincerity and very practically grounded perspective came across clearly, and I'm pleased that your curiosity has been sparked.

I was fortunate to enjoy regular access to Are and it took me many years to eventually grasp his subject to the point of being able to see only a part of what he saw and discuss it.  But in the beginning it was so esoteric that it was nearly incomprehensible.

My intention was to elaborate further and to volunteer Are's credentials as an authority for the sake of the greater readership which includes a healthy constituent of the justifiably dubious, and a troll here and there (hence the link, for its list of papers he authored).  Many of us play with theories and do experiments but Are's significant professional responsibilities were in large part founded on his knowledge and research of fractography, which had grown out of his devotion to flintknapping.  In response to questions he posed in the '70s to Crabtree and Tixier, they encouraged him to find the explanations which set him on this path.   
Quote
Like
Share

toxophileken
Registered User
toxophileken
Registered User
Joined: January 15th, 2006, 4:55 am

July 10th, 2018, 11:03 pm #11

Super stoked on the great info and level of discourse!  Thanks guys!

And thanks for the link, Forager!

Ken
Quote
Like
Share

toxophileken
Registered User
toxophileken
Registered User
Joined: January 15th, 2006, 4:55 am

July 10th, 2018, 11:05 pm #12

As long as I'm here, I'll note that yesterday I was soaking in the pool to cool off, and noticed that I could see well enough through the water that I thought I could probably find my platform without a dive mask, and might be even able to work on platforms that way.  If not, I figure I could prepare the platforms above water, in a pinch.

Ken
Quote
Like
Share