Needed: Word for small wrinkles that look like Divitrification!!

[willyoung]

When you make drastic bends while minipulating glass, sometimes you bend the glass a little bit more than the surface of the glass would like you to. :twitch:
This causes very small wrinkles on the surface of the glass. While foggy, and similar looking to Divitirication in appearance, This is NOT divitrification! :wes:
These small wrinkles can be removed by reheating the surface of the glass untill it is molton. Divitrication is the crystallization of glass on the molecular level, and is inreversable (although I've heard sea salt can help).

I know that most of you are aware of this, and have also seen how it has become very commonplace to refer to these wrinkles as divitrification. I believe this is due to the fact that theres is not a term, (word, name) for this borosilicate characteristic. (I assume that with soft glass, this problem is next to non-exsitent).
I thought that it might be fun to try and invent a word for this borosilicate phenomonon!!!! It might eventually lead to people being able to communicate their proplems they are experiencing with less confusion!:D

Everyone knows that if making it molton makes it go away, its not Divitrification!

So, I appoligize in advance if I am unaware of the proper termanology for this, and if not, lets be creative and see what we can come up with!

Here's my contribution: (I know someone has got sometHing more creative than this):

CHILL WRINKLES!!!!
COLD STIFF SKIN C.S.S.
THE INSIDE OF MY BEND LOOKS LIKE YOUR GRANMAS BEHIND!!

[harpentuan]

Your freaking me out man.

[Swampy]

prepuce (http://en.wikipedia.org/wiki/Foreskin)?

[somewhere]

Ok first off it's spelled devitrification.
I have always been told compressing cold glass will cause devitrification this is coming from the old scientific blowers with more experience and knowledge then I'll probably ever have.

Read this:


TECH REPORT: Devitrification of glass

MICHAEL OLSEN
Research Glassblower
Colorado State University
Department of Chemistry
Ft. Collins CO 80523-1872
(970) 491-5229 (voice)
(970) 491-1801 (FAX; attn. M Olsen)
glassguy@lamar.colostate.edu


Q: What is devitrification, how does it happen, and how can it be prevented?

A glass is by definition a liquid at all temperatures. Compositionally a typical glass consists of the 'glass (or network) formers' (SiO2 and B2O3), fluxes (also called alkaline metals, K2O and Na2O), and the network (or matrix) modifying alkaline earths (CaO, BaO, PbO, ZnO).

Other oxides capable of glass network formation include GeO2, P2O5, As2O5, As2O3, Sb2O3, and to a limited degree V2O5, ZrO2 and Bi2O3. The oxides of Ti, Zn, Pb, Al, Th and Be can be included in varying concentrations, but will not on their own, yield a glass. These, and other oxides that will not form a glass (including Sc, La, Y, Sn, Ga, In, Mg, Li, Sr, Cd, Rb, Hg, and Cs) are used as network modifiers.

Within the glassy matrix there are bridging oxygen ions and non-bridging oxygen ions (which ionically bond to the cations Li+, Na+, K+ or Ca++ in a typical glass). Technically, glass is a metal oxide polymer with SiO2 being the principal copolymer of all commercial glasses. In three dimensions, this polymer can be depicted as a random 'cobweb' of silicon ions each bonded to either three or four oxygen atoms. Progressing along any branch of the polymer chain we see Si-O-Si-O-Si-O-Si-O with an occasional matrix modifier ion (as Pb, lead) substituting for a Si. Branching from each Si will be another similar chain of O-Si-O-Si-etc. Occasionally, a chain will terminate at a non-bridging oxygen, which has a strong negative charge. This oxygen will be protruding into a microscopic cavity in the glassy matrix within which resides a counterbalancing, positively charged alkaline metal flux ion (as Na+, sodium).

A pure SiO2 glass is called fused quartz. It can be manufactured from rock quartz crystals, and has no flux nor matrix modifiers within it. Because of the uninterrupted strength of the Si-O bonds it yields a very high temperature softening ('hard') glass. Occasional interruptions of the Si-O matrix with modifying ions (with weaker metal-O bonds) will lower the viscosity profile of (or, 'soften') the glass. The more alkaline earth oxides added to the glass, the more the viscosity profile is depressed.

This is glass when everything 'goes right'. When glass devitrifies, it doesn't necessarily revert to its former, solid, crystalline constituents. In many instances a devitrified glass will not be chemically altered, but rather it will crystallize into its ceramic analogue.
Q: Is it true that devitrification can happen after prolonged stressing and exposure to contaminants and this in turn will result in a degradation of physical properties?

First, the jargonal term for devitrification is 'devit'. The term however describes more than one phenomenon.

Yes, both stress and surface contamination both result in what is termed devit, however I have never read nor heard a discussion of the former, and I honestly don't remember where I 'learned' of the decompositional (reductional or oxygen liberating) role I describe in a document discussing the role of oxygen in glass - I don't think I have anything in print that I can reference, so what follows is largely conjecture.

I have a theory about stress induced devit, and I'd appreciate any input outlining prior experiments conducted to test it.

First, it is commonly observed that a piece of glass, when heated to the point where it is somewhat plastic but not yet at its 'working point' (these glassworking points - including strain and annealing - are all best defined by specific viscosities) will exhibit a surface 'defect' termed 'devit' when a compressive or flexing force is applied. This devit commonly appears as a milky haze on only (a hint!) the outer surface of the workpiece, however it may also appear as a surface crazing.

In the experience of most glassblowers, the milky haze devit is reversible by 'burning' it back into the bulk - e.g. focused heating. It is 'common knowledge' among glassblowers that this burning procedure 're-melts' the devit. As discussed below, I do not agree with this.

The craze-type devit is a little more troublesome, as the repair procedure is the same however the fix is not always successful as there may be some 'wrinkles' in the glass that remain no matter what is done once they somehow become 'fixed' in the glass. The only thing that can then be done is to cut out, grind off, or (with a torch) 'pick' these defects from the surface of the workpiece.

As a result of 20+ years experience, I have observed that certain repair procedures for this 'stress-induced devit' are more successful than others, and I have now developed techniques which nearly always avoid inducing the phenomenon in the first place, and a repair procedure to reverse the phenomenon that is nearly 100% successful. But first, here are a couple of additional points that I think relate to the surface-devit phenomenon:

I do not recall ever seeing the milky haze devit in quartz (not to be confused with 'bloom').

I have induced 'wrinkles' in under-heated quartz, but I do not recall seeing quite the surface crazing that 'softer' (alkaline flux-containing) glasses commonly suffer from.

It is my impression that softer glasses are more prone to irreversible stress devit than the harder glasses. This needs to be tested. If true, it would strongly support my hypothesis of what underlies the phenomenon.

'Flame cutting' a piece of glass will often produce a quartzlet if the freshly 'torn' edge is exposed directly to a sharp (very hot and O2-rich) flame.

All of these phenomena can be diminished or avoided entirely if the effected glass is simply not exposed to a sharp flame! The 'devit' will simply flow back into the bulk.

MY HYPOTHESIS: Stress-induced devit is only indirectly induced by applied force and actually has little to do with either the force (stress) or deformation (strain). The minute surface geometric irregularities which are formed by applied force (wrinkles in regions of compression and crazing in regions of tension - neither of which affect the bulk structure of the glass) merely increase the surface to volume ratios of the outer few microns of the glass which allows these so-called 'devit' micro-structures to become super-heated by the flame, allowing the higher vapor pressure fluxes to volatilize, thus creating a harder, more quartz-like glass. Note specifically that what I am asserting is that stress-induced devit is not a form of devit at all but a form of chemical decomposition at the surface which results in a different glass!

If my hypothesis is true, it should be easily testable.

http://www.chm.colostate.edu/~glass/devit.html

[Hefe]

stress?

[mer]

...A glass is by definition a liquid at all temperatures.
http://www.chm.colostate.edu/~glass/devit.html

a lot of that was over my head and i'm not disagreeing with the premise of the article but this first line didn't inspire confidence.

[Kool]

a lot of that was over my head and i'm not disagreeing with the premise of the article but this first line didn't inspire confidence.

I didn't even read that long thing, but I don't think I would necessarily disagree with the statement that "glass is by definition a liquid at all temperatures."

Is an ice cube liquid or solid? Or a liquid that is temporarily in a solid state?

[mer]

i was always taught that water is a solid, liquid and a gas depending on the environment. there was a good link about this liquid glass myth in another thread recently, i'll dig. edit coming.

informative but not definitive;
http://math.ucr.edu/home2/baez/physics/General/Glass/glass.html

[Kool]

Interesting link. This part especially pertains to what we are talking about:

"It is sometimes said that glass is therefore neither a liquid nor a solid. It has a distinctly different structure with properties of both liquids and solids. Not everyone agrees with this terminology."

and this part:

"For crystalline substances the distinction between the solid and liquid states is very clear, but what about glasses? Indeed, where do polymers, gels, foams, liquid crystals, powders and colloids fit into this picture? Some people say that there is no clear distinction between a solid and a liquid in general. A solid, they claim, should just be defined as a liquid with a very high viscosity. They set an arbitrary limit of 1013 poises above which they say it's a solid and below which it's a liquid.

According to another point of view, this ignores a distinction between viscosity of liquids and plasticity of solids. An ideal Newtonian liquid deforms at a rate which is proportional to stresses applied and its viscosity. For arbitrarily small stresses a viscous liquid will flow. Molasses, pine pitch and Silly Putty are examples of liquids with very high viscosity which flow very slowly under only the force of their own weight. On the other hand, plastics can be very soft but are still considered solid because they have rigidity and do not flow."

and finally:

"There is no clear answer to the question "Is glass solid or liquid?". In terms of molecular dynamics and thermodynamics it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid. The difference is semantic. In terms of its material properties we can do little better."

Oh man, this thread got way off track, huh?

Glassantics suggestion was a good one, "stress" pretty much covers it all.

but, ummmm, how about "Divrinkles"?

[jane clifton]

I always just called them "stretch marks".

[phab]

...yeah stretch marks is what they look like, thats what ive always called them. can we think of a good name for that space between here and there? im getting tired of calling it space.

[David Sandidge]

"Prepruce" that's funny shit!

Science has classified glass as an "amorphic solid" it cas no cystaline stucture as other solids have. The molicules line up randomely. It is neither a liquid or a solid. Glass is in a catagory all by itself.

These wrinkles described by willyoung are caused by the high viscosity or stiffness of the glass as it is being manipulated. It becomes a high stress point and will eventually crack if not annealed. If the glass is forced even harder as the viscosity is increased more, it will result in a crack which is the separation of the molecular structure between the electron and the nucleous. The cracking is called "cleaving" and it will follow a random path because there is no crystaline structure to follow. This is not devitrification. Devitrification does not cause cleaving. If the glass is not pushed to the breaking point, it can be annealed which will allow the release of the energy which has been trapped within the molecule. The wrinckes will then not be stressed. These wrinckles can occur in any type of glass, hard or soft, any COE.

Devitrification is "phase separation" which is the re-crystalization of the molecular structure of the components of glass. The fluxes or binders which is the soda and boron are no longer doing their job. By using salt (sodium), the flux is reintroduced. This is not stress and does not cause cleaving.

I would and have simply referred to these wrinkles as stress wrinkles because that is exactly what they are.

This is how I understand stress and devit. If I am incorrect about any of this I hope that someone will clarify for me.

[Kool]

...Science has classified glass as an "amorphic solid" it cas no cystaline stucture as other solids have. The molicules line up randomely. It is neither a liquid or a solid. Glass is in a catagory all by itself...

Did you read the link Mermonkey put up? It's interesting, and the author covers what you say, but concludes that "it is possible to justify various different views that it is a highly viscous liquid, an amorphous solid, or simply that glass is another state of matter which is neither liquid nor solid."

[newmexicomagma]

ive heard people call it mechanical devitrification.

[willyoung]

thanks somewhere,
theres some really interesting information here. This is the in depth explination of what I am talking about. Notice that he does make a distinction between two different effects of compressive or flexing force.

One appears as a surface haze, and the other appears as an actual surface crazing. I would make the distinction between the two as haze being an inavoidable part of some shaping processes which can be corrected, where as the later is actual small wrinkles which appear on just the surface due to the application of two much compressive or flexing force during the shaping process.

I agree the the haze can be merely burned off with ease, where as actual wrinkles are much more prone to devitrification due to the increase of surface to volume ratios. Just as you could easily burn, or devitrify, a small bleb or bump that is not yet melted into the mass by using an overly agrresive flame.

As for his hypothesis, I would agree that on a molecular lever, there are times that the glass has not been devitrified (no development of crystaline molecular structure) and will still behave differntly. Although still amorphous in structure it will begin to behave differently than the rest of the glass due to slight chemical decomposition ( the lose of fluxes due to an overheating of the glass, resulting in a slightly harder glass on the surface).

Furthermore, I would like to state that I can agree that while difficult to notice, even the simple haze which can be remelted with ease might be chemically different than the rest of the glass after remelted. I believe that this is his point. Which is proven by a more extreme example when the surface is visibly wrinkly, often difficult to repair without noticing that the glass is behaving differnetly than the glass around it.

I am always interested in this type of information, I love knowing whats happening on a molecular level!!:D

I hope my explinations not confusing......It's only what I got from the article correct me If I'm wrong.
I was hoping that my summary might help someone who got bored with all the technical data.....

thanks aqain somewhere.........!!!!

I would love to hear other peoples interpretation of this article.....
:nerd:

[richsantaclaus]

I thought they were called "chill marks"

[willyoung]

prepuce....hahaha... ROFL!!!!
thanks swampy!
thats more the type of response I was expecting!!!

So far names for strech marks:

1. Prepuce
2. Divrinkles (my favorite so far)
3. Strech Marks
3. Stress Wrinkles
4. Mechinical devitrification (??) not sure that works for me
5. Stress
6. Chill marks

[Mac Maestro]

I thought that's just what happens to glass after it's in the bathtub for too long.



The way Sandidge explains it is pretty much what I've been taught.



SO if we are just assigning a random word to the stretch marks to see if it will stick, I vote making a noun out af a verb and calling it corrugate. (CORE-uh-get) -It's Corrugated glass- call it corrugate.


Here's the VERB we can manipulate:
cor·ru·gate verb, -gat·ed, -gat·ing, adjective
–verb (used with object) 1. to draw or bend into folds or alternate furrows and ridges.
2. to wrinkle, as the skin or face.
3. Western U.S. to make irrigation ditches in (a field).
–verb (used without object) 4. to become corrugated; undergo corrugation.
–adjective 5. corrugated; wrinkled; furrowed.

[roger parramore]

The old definition of glass as a liquid has really given way to something like this: Glass was long considered a liquid with solid properties. It is now much more commonly referred to as a solid with liquid properties. Take your pick. Does it really matter. Glass wa glass desu. (Glass is glass). Though you were taught there are three states of matter--solid, liquid, gas--there is another state of matter: The glassy state. Glass is a stuff of its own. It really makes much more sense to treat it this way rather than try to describe it according to definitions that by definition don't work. By the way, how about "microwaves" for the little folds.

[FredLight]

+1 Corrugate.

I like it. It wouldn't have worked without those definitions.

[Swampy]

What David said and Rich


I thought they were called "chill marks"

when I whack a white hot glob straight onto the marver and hold it there till the glow goes off, the contacted area will look like it has ridges like water ripples, going out from the centre. Sometimes see it on a mould-blown jar or bottle too.

That's chill marks to me but let me know if I need straightening out and I'll get the missus to flog me relentlessly till I get it right.

[richsantaclaus]

Well, I went asking several soft glass people and they said "chill marks" like the ones you so nicely describe as ripples like a drop of water in a pond radiating outward.

[Brian Newman]

Though you were taught there are three states of matter--solid, liquid, gas--there is another state of matter: The glassy state.

Plastic is the word for what you refer to as "the glassy state". Also you neglect to mention the plasma state, the state beyond gas.

[roger parramore]

Actually I intended to say the glassy state, easily googled, which is different from plastic or rubbery state. And I didn't restrict other states of matter. I merely said there is another. Is the plasmatic state coherent to this thread? I don't know, maybe.

[Mr. Whale dick]

i call them strech marks

[Brian Newman]

I used google, and it seems glassy state is the more common term. I was basing my comment on an article from an ASGS fusion magasine from the fifties or sixties.

Blowsy glassy.

[michaelangeloglass]

O.k. I really didn't want to get into this but heres the deal....

All of this happens because your not working the glass hot enough, making the moves connectoins fast enough, like a machine!!!


I think it might help if you get mad at the glass, maybe look right @ the piece and tell it "you are nothing, and you'll do what I say"


You have to figure because we have the technology doesn't mean we have to go getting soft!


lol


Heres the real deal if you stretch, twist, or pull the glass at a low temp to many times it will start changing its formula, of physical compounds.

So what I was saying above is somewhat true, but I would really say that it's an issue with atmosphere, or temp.


Keep it Hot!!!

[SouthernFume]

the stretch marks are called stress. it happens when the glass is not hot enough to mold,shape, or whatever you are doing. to make it go away you just simply reheat enough to make them disappear. if ur point is open at the end, i usually put an earplug or cigarette in the end to keep the heat. it works really well.

[J Howard]

crappy heat base indicators? beginner's lack-o-luck marks? tard wrinkles....

[jr23]

Did someone mention penis wrinkles! I usualy have a few wrinkles tell its time for action. Try blowing on them! That's what always gets rid of mine.

[BlueLilyStudio]

I think we call those stretch marks: "youneedtobuffthatshitout" around here, but it is a bit wordy.

[FiredDesires]

Rich....have you ever worked the soft glass EDP? You know that chalky haze that ends up on it? That is what this stuff they're talking about appears like, minus the wrinkles ...I've only seen it on boro and when it is in my in-experienced hands trying to bend and shape a clear rod, lol. It looks like its' been acid etched too....probably all the acidity of the glass vomit, cause all that twisting, stretching, pulling & turning? Surely will make the glass throw up eventually!

[Tsnider]

this thread kicks ass. im a newb and was wondering why tf this was happening to my pieces. glas i can fix the problem, or at least try to prevent it!
thanks guys

[Thomas Grimmett]

It's called mechanically induced phase separation, but here at Glass Alchemy we call it MIPS. Phase separation is when the glass “un-mixes” into pools of borax, alumina, and silica (those are the wrinkles). Mechanically induced means that it was forced during the stretching (the glass was not hot enough when it was manipulated... try stretching vertically rather than horizontally and gravity will tell you when to stop).

There are many different forms of devitrification and this is one of them. Getting a metallic luster on the surface or unwanted “haze” is also a form of devitrification.

Thomas

[NUBBLET]

lets call it Stiltskin

[Icarus]

I vote for "let's not worry too much about what it's called, and just deal with fixing it".

[Kevin Bumble]

yha Icarus, to fix it you need a pin flame and don't over heat the spot you are working on you don't want to melt or change wall thickness or distort the whole thing. don't create a name for it fix it. yes this is caused by stressing/forcing the glass when it is cooling probably too cool.