BORO
08-06-2015, 01:29 AM
The ninjas have been coersing in the dark again.
It seems like occasionally we get confusion between the two terms, what they are, and why it happens.
Sometimes it's a noob mistake, some times it's just lazy mixing of terms. (Guilty)
I happen to have a good example of what each one looks like. Fyi They are not the same, most important to know the difference, it will save you time, and headache.
Here is a epic fail. It was on its way to becoming a flint lock style pirate gun bub.
This picture shows the cracked side. The cracks are clean, they seem to go all the way through. This side may heal fine in a flame, Over working it (healing the cracks) may lead to Coe blow out in the end. ( checking)
In this picture tho, only standard cracks. (And some fiber blanket dust)
77097
You can tell a true crack VS. separating layers from checking. The standard crack goes all the way through most times, you can feel it with a finger on the surface. It's usually solo. Or splits into a few crack lines. If your not sure, chances are it's a true crack that can be fixed. (Melted back in) Weather or not it heals clean is user controlled . Do it clean, no one can tell, even the most experienced blower. Do it not so well, you may get a line of tiny trapped air bubbles . Imo, the glass is still strong, just uglier . If you flail, it may split apart, or just turn to scrap bucket shat. Healing cracks right in a kiln, or after a hot (1100) soak, may increase your success rate. As long as it's not true Coe separation , (checking) I think anything can be saved. It may not be pretty, but it's in a single piece.
77098
Now let's talk about the dreaded check/ color separation. It looks much more like " crackle glass" . The cracks will be under the surface, still smooth to the touch. Extreme c.o.e. Blow out (checking) may also create true cracks along with the sepation blow out. If you attempt to fix the checking, it will melt in and heal when hot. However it reappears after the kiln cools off.
Here is a c.o.e. Checked ball.
77100
Don't confuse occasional shalow stress cracks in your clear. You can get micro stress cracks on the surface of some clear. It is a shallow crack, only on the face of the clear, with more clear below. Theat type of stress crack may heal real easy. They way I can tell the difference, usually they are all alone, just a solo shallow crack. imo, they are from heating too fast/ unevenly, they appear to look like c.o.e. but it is shallow, and runs all alone like a standard crack does. If your not sure, try to heal it. It takes a second, you have little to lose, much to gain.
True c.o.e. Is usually between two types of glass. It's usually very easy to tell. (Color and clear, or color and color ) right where they meet. Here is a example of i.s.o. That had unfixable c.o.e. Issues. You can see the clear is happy, unaffected. But the differences between the plum kush, and the clear, were obvious. No reason to try to fix it. Just a time waster.
77109 77110
If your looking at that,and thinking "I can fix that" I beg to differ....., let's get back to that e.b.v ball as a example...
77100
Kilned it , Now let's melt it in, good and hot. Heal all that bull s#*¥! , let it kiln cycle again , trying my best to save it,
Comes out of the kiln and........ Oh no.
77101
As you can see, it appears totally different, the stress is pushed around, but the cracks return.
Now, let's check out the difference between the two types, on one piece.
Remember that bubbler ? 77102 it's "real" cracks....
Check out the other side. Same exact piece, worked the same way, but....
77103
You can really see the checking, the cracks are mostly under the surface, running parallel , right where the two colors (or color and clear ) meet.
77104
Why it happens (checking) is a debate. Lots of reasons why it can happen. I find much less info on what you can do to keep it at bay.
As far as I can tell, three real reasons why checking happens. (iMO)
#1. The most common, is differences in c.o.e, (how much your chosen glass expanded when hot and shrinks when cool.) If you were to melt a beer bottle , and boro together. Its all is fine when heated. The two types of glass fit together perfectly when they are still hot, in a expanded state. All is well.
The beer bottle, let's say it's at a "10" when its expanded, the Boro is at a "10" as well. It all fits like a puzzle piece.
As it cools off, the beer glass shrinks more. (Let's say it shrinks to a 5 when cool) The boro also cools. But the boro only shrinks to a "8". Now the two no longer fit together. They are two totally different shapes right where they meet. You get the checking c.o.e. Blow out where the two types join one another.
#2. Checking can happen when you get changing c.o.e between two colors , or clear and color. It occurs when you over heat, or over work certain color combos. Some colors just don't like to play with others , due to "#1." (Different c.o.e.s) or a change in c.o.e, after a long work cycle, it DID work but it doesen't anymore. One of the glasses changed.
#3,you get phase separation (glass breaks down into ingredients ) or crystals on the layer where they meet. This results in "#1." C.o.e changes. I feel like #2, and #3 are similar, but not the same exactly. #3 can also occur from viscosity differences. (I know the least about viscosity )
............ Not so much about cracks, but......................
The only other stress maker, is from pushing the glass around. Let's say you make a mouth piece hole. If you reem it out, then heat it some, on everyside of the hole, you take the stress you just introduced with the reemer back out of the glass.
If you heated the mouth hole, then reem it that perfect amount right before it goes away, you need a long hot kiln soak to take away that stress you introduced right at the end.
Same thing goes for a wield. You Join two sections together , Then adjust the angle of the two, after you buff out the wield. You added stress. ( = Less success ) it's better to get it melted clean, adjust the angle , THEN , at the end you heat up all the sides evenly, carefully keeping the wield strait and true but glowing hot. That last soaking heat relieved any stress you introduced by mechanically pushing the glass around. Even the "north south east west" melting in a 1/4 connection at a time, doesent remove the stress the same way as heating it all at once. When it's all hot, it lets the glass pull on/ pull out that stress, and reduce it however the hot glass wants it to be.
If you take the stress out with the torch, you will almost never have true cracks appear to begin with. It's Captain obvious, however I said the last part about "adding stress by shaping , removing by heating" to my lady last week. Almost got murdered. it's obvious, but "no one ever told her." Even with longer work cycles, and colder glass. Once you remove the stress , As long as you don't jump to cold areas, heating it back up too fast, your good. Heat is your friend, work it hotter , with a smoother heat gradient to the cool areas. All makes less stress, and smoother shapes.
.................................................. ...............
Some of the things you can do to prevent it checking?
I like to think about surface area in a given piece of prep.
Let's stick with the blue velvet. It's a cobalt over a sparkle green. The stock tube you bought, has stress in it already. It comes from the initial heating. It can also be from the pulling /stretching of the tube. Some one bends it when hot, during production, it will have more stress. It also will come with a certain amount of crystal growth right where the colors meet. I think of that surface area like this.,,
When it's in that tube you bought, it has a certain amount of crystals. Shown here in this drawing (each dot) it's 10# of sh*#¥ in a 10# bag. We good.
77105
Now you take that tube, and work it. You try, but most likely you add even more crystals, increasing the chances of incompatibility. The bigger issue, you reduce it nice and thick, you decrease the surface area between each color, but it has the same amount of crystallization , maybe more from working. You get that 10-12# s of sh*#¥ in a 5# bag. The risk is increased.
It ends up looking like this. 77106
You can see you have more crystallization in a smaller area. for that reason, (opinion) if you are diligent , and keep the finished wall thickness thinner than the tube of prep, your good 90% of the time. (Assuming you worked correctly , and used slow heat, lots of O2.) Reduction can also add more crystallization/ phase separation? I took the last tip to heart. It fixed 90% of any checking I had in the past. Covering e.b.v in comb dots, still screws me. (Viscosity ? Cobalt I.r.? )
.................
Lots of info will tell you too high a kiln temp, and you can create checks. I have seen a lot of people swear by this. (Run 950 with sparkle colors, not 1050) seems like it must be true? My experience, I know I have run long hours/days at 1075-1100 analog , with no issues. Only if it sits right on the elements, it gets Pissy in that area. Although I have not seen it, a lower kiln temp can be the difference for a lot of peeps.
http://www.taglass.com/Articles.asp?ID=259
Working check prone color wrong, (green /cromiuum) It can kick your success rates right in the teeth. Jason Howard said it best.....
77107
As far as viscosity , effecting the checking. It's hard to find any real info. I know the g.a. Resource page has some good info to read.
http://www.glassalchemy.com/article_list
I know Jason touched on how viscosity can play a role. I'm still looking for the hot tips I remember , talking about viscosity (g.a. resource page, and ? And? The color awareness group? ) ,,, I would like to know more, and I leave you with lots of un answered questions.
Hopefully some answers to ponder as well.
77108
Like the last quote, lots of options if your aware. I know I can heat up e.b.v. Right off the bench successfully. I also know it adds more stress from heating the outer faster than the inner layer. If I kiln the tube up to temp, so the inner, and outer are heated at a similar rate, starting in the flame when it's above the strain point, I give the glass what it wants. (Higher rate of success )
I never had success with China jade. (green or white) I found out a new popular color uses the jade white as a base. I asked the guy batching the color how his success rate is? He says great, just about 100%.... (Insert myself, talking trash on jade.) He asked if I flame polish each end, and annel the tube one half at a time first. (Only 1/2 fits in my kiln at one time) he said they don't bother to anneal the white/import stuff. I took his advise , and it's super stable now. Proof it's what you know , that can make all the difference.
May be why I'm addicted to t.m.p. read up, increases your success.
Here is some more good info on c.o.e. http://www.talkglass.com/forum/showthread.php?43082-The-science-of-checking
..................
Anyone with viscosity info, or links, I'm all ears. Any mistakes, please feel free to comment.
This is mostly my opinion from what I experience day to day full time working glass.
It may be right, or wrong, but thinking about the glass In a way that helps you succeed is the key.
Keeping terms correct, so others can follow, essential .
It seems like occasionally we get confusion between the two terms, what they are, and why it happens.
Sometimes it's a noob mistake, some times it's just lazy mixing of terms. (Guilty)
I happen to have a good example of what each one looks like. Fyi They are not the same, most important to know the difference, it will save you time, and headache.
Here is a epic fail. It was on its way to becoming a flint lock style pirate gun bub.
This picture shows the cracked side. The cracks are clean, they seem to go all the way through. This side may heal fine in a flame, Over working it (healing the cracks) may lead to Coe blow out in the end. ( checking)
In this picture tho, only standard cracks. (And some fiber blanket dust)
77097
You can tell a true crack VS. separating layers from checking. The standard crack goes all the way through most times, you can feel it with a finger on the surface. It's usually solo. Or splits into a few crack lines. If your not sure, chances are it's a true crack that can be fixed. (Melted back in) Weather or not it heals clean is user controlled . Do it clean, no one can tell, even the most experienced blower. Do it not so well, you may get a line of tiny trapped air bubbles . Imo, the glass is still strong, just uglier . If you flail, it may split apart, or just turn to scrap bucket shat. Healing cracks right in a kiln, or after a hot (1100) soak, may increase your success rate. As long as it's not true Coe separation , (checking) I think anything can be saved. It may not be pretty, but it's in a single piece.
77098
Now let's talk about the dreaded check/ color separation. It looks much more like " crackle glass" . The cracks will be under the surface, still smooth to the touch. Extreme c.o.e. Blow out (checking) may also create true cracks along with the sepation blow out. If you attempt to fix the checking, it will melt in and heal when hot. However it reappears after the kiln cools off.
Here is a c.o.e. Checked ball.
77100
Don't confuse occasional shalow stress cracks in your clear. You can get micro stress cracks on the surface of some clear. It is a shallow crack, only on the face of the clear, with more clear below. Theat type of stress crack may heal real easy. They way I can tell the difference, usually they are all alone, just a solo shallow crack. imo, they are from heating too fast/ unevenly, they appear to look like c.o.e. but it is shallow, and runs all alone like a standard crack does. If your not sure, try to heal it. It takes a second, you have little to lose, much to gain.
True c.o.e. Is usually between two types of glass. It's usually very easy to tell. (Color and clear, or color and color ) right where they meet. Here is a example of i.s.o. That had unfixable c.o.e. Issues. You can see the clear is happy, unaffected. But the differences between the plum kush, and the clear, were obvious. No reason to try to fix it. Just a time waster.
77109 77110
If your looking at that,and thinking "I can fix that" I beg to differ....., let's get back to that e.b.v ball as a example...
77100
Kilned it , Now let's melt it in, good and hot. Heal all that bull s#*¥! , let it kiln cycle again , trying my best to save it,
Comes out of the kiln and........ Oh no.
77101
As you can see, it appears totally different, the stress is pushed around, but the cracks return.
Now, let's check out the difference between the two types, on one piece.
Remember that bubbler ? 77102 it's "real" cracks....
Check out the other side. Same exact piece, worked the same way, but....
77103
You can really see the checking, the cracks are mostly under the surface, running parallel , right where the two colors (or color and clear ) meet.
77104
Why it happens (checking) is a debate. Lots of reasons why it can happen. I find much less info on what you can do to keep it at bay.
As far as I can tell, three real reasons why checking happens. (iMO)
#1. The most common, is differences in c.o.e, (how much your chosen glass expanded when hot and shrinks when cool.) If you were to melt a beer bottle , and boro together. Its all is fine when heated. The two types of glass fit together perfectly when they are still hot, in a expanded state. All is well.
The beer bottle, let's say it's at a "10" when its expanded, the Boro is at a "10" as well. It all fits like a puzzle piece.
As it cools off, the beer glass shrinks more. (Let's say it shrinks to a 5 when cool) The boro also cools. But the boro only shrinks to a "8". Now the two no longer fit together. They are two totally different shapes right where they meet. You get the checking c.o.e. Blow out where the two types join one another.
#2. Checking can happen when you get changing c.o.e between two colors , or clear and color. It occurs when you over heat, or over work certain color combos. Some colors just don't like to play with others , due to "#1." (Different c.o.e.s) or a change in c.o.e, after a long work cycle, it DID work but it doesen't anymore. One of the glasses changed.
#3,you get phase separation (glass breaks down into ingredients ) or crystals on the layer where they meet. This results in "#1." C.o.e changes. I feel like #2, and #3 are similar, but not the same exactly. #3 can also occur from viscosity differences. (I know the least about viscosity )
............ Not so much about cracks, but......................
The only other stress maker, is from pushing the glass around. Let's say you make a mouth piece hole. If you reem it out, then heat it some, on everyside of the hole, you take the stress you just introduced with the reemer back out of the glass.
If you heated the mouth hole, then reem it that perfect amount right before it goes away, you need a long hot kiln soak to take away that stress you introduced right at the end.
Same thing goes for a wield. You Join two sections together , Then adjust the angle of the two, after you buff out the wield. You added stress. ( = Less success ) it's better to get it melted clean, adjust the angle , THEN , at the end you heat up all the sides evenly, carefully keeping the wield strait and true but glowing hot. That last soaking heat relieved any stress you introduced by mechanically pushing the glass around. Even the "north south east west" melting in a 1/4 connection at a time, doesent remove the stress the same way as heating it all at once. When it's all hot, it lets the glass pull on/ pull out that stress, and reduce it however the hot glass wants it to be.
If you take the stress out with the torch, you will almost never have true cracks appear to begin with. It's Captain obvious, however I said the last part about "adding stress by shaping , removing by heating" to my lady last week. Almost got murdered. it's obvious, but "no one ever told her." Even with longer work cycles, and colder glass. Once you remove the stress , As long as you don't jump to cold areas, heating it back up too fast, your good. Heat is your friend, work it hotter , with a smoother heat gradient to the cool areas. All makes less stress, and smoother shapes.
.................................................. ...............
Some of the things you can do to prevent it checking?
I like to think about surface area in a given piece of prep.
Let's stick with the blue velvet. It's a cobalt over a sparkle green. The stock tube you bought, has stress in it already. It comes from the initial heating. It can also be from the pulling /stretching of the tube. Some one bends it when hot, during production, it will have more stress. It also will come with a certain amount of crystal growth right where the colors meet. I think of that surface area like this.,,
When it's in that tube you bought, it has a certain amount of crystals. Shown here in this drawing (each dot) it's 10# of sh*#¥ in a 10# bag. We good.
77105
Now you take that tube, and work it. You try, but most likely you add even more crystals, increasing the chances of incompatibility. The bigger issue, you reduce it nice and thick, you decrease the surface area between each color, but it has the same amount of crystallization , maybe more from working. You get that 10-12# s of sh*#¥ in a 5# bag. The risk is increased.
It ends up looking like this. 77106
You can see you have more crystallization in a smaller area. for that reason, (opinion) if you are diligent , and keep the finished wall thickness thinner than the tube of prep, your good 90% of the time. (Assuming you worked correctly , and used slow heat, lots of O2.) Reduction can also add more crystallization/ phase separation? I took the last tip to heart. It fixed 90% of any checking I had in the past. Covering e.b.v in comb dots, still screws me. (Viscosity ? Cobalt I.r.? )
.................
Lots of info will tell you too high a kiln temp, and you can create checks. I have seen a lot of people swear by this. (Run 950 with sparkle colors, not 1050) seems like it must be true? My experience, I know I have run long hours/days at 1075-1100 analog , with no issues. Only if it sits right on the elements, it gets Pissy in that area. Although I have not seen it, a lower kiln temp can be the difference for a lot of peeps.
http://www.taglass.com/Articles.asp?ID=259
Working check prone color wrong, (green /cromiuum) It can kick your success rates right in the teeth. Jason Howard said it best.....
77107
As far as viscosity , effecting the checking. It's hard to find any real info. I know the g.a. Resource page has some good info to read.
http://www.glassalchemy.com/article_list
I know Jason touched on how viscosity can play a role. I'm still looking for the hot tips I remember , talking about viscosity (g.a. resource page, and ? And? The color awareness group? ) ,,, I would like to know more, and I leave you with lots of un answered questions.
Hopefully some answers to ponder as well.
77108
Like the last quote, lots of options if your aware. I know I can heat up e.b.v. Right off the bench successfully. I also know it adds more stress from heating the outer faster than the inner layer. If I kiln the tube up to temp, so the inner, and outer are heated at a similar rate, starting in the flame when it's above the strain point, I give the glass what it wants. (Higher rate of success )
I never had success with China jade. (green or white) I found out a new popular color uses the jade white as a base. I asked the guy batching the color how his success rate is? He says great, just about 100%.... (Insert myself, talking trash on jade.) He asked if I flame polish each end, and annel the tube one half at a time first. (Only 1/2 fits in my kiln at one time) he said they don't bother to anneal the white/import stuff. I took his advise , and it's super stable now. Proof it's what you know , that can make all the difference.
May be why I'm addicted to t.m.p. read up, increases your success.
Here is some more good info on c.o.e. http://www.talkglass.com/forum/showthread.php?43082-The-science-of-checking
..................
Anyone with viscosity info, or links, I'm all ears. Any mistakes, please feel free to comment.
This is mostly my opinion from what I experience day to day full time working glass.
It may be right, or wrong, but thinking about the glass In a way that helps you succeed is the key.
Keeping terms correct, so others can follow, essential .