Boro Question Marbles

love2shoot · #1 2012-01-02, 5:16pm

Hello all im new to lampworking and boro Ive made a couple of items and i prob know the answer to this but i had different expertations of boro.

Ive made 2 items with boro and cooled them with vermulicite so i could batch anneal them. I made a implosion pendant and a marble. Both items when lifted from the verm. had cracks in them. Now im not sure if i can fix them the pendant exploded when i tried to very slowly reheat it. The marble i havent tried yet.
Here is a picture of the marble.
http://www.lampworketc.com/forums/al...pictureid=5013
[url]http://www.lampworketc.com/forums/album.php?albumid=575&pictureid=5012[/url

I am unsure why these are cracking. If you have any ideas please help. I do know that the pieces should be annealed right away but i do fusing projects also and sometimes my kiln is in use. and while im waiting for the kiln my pieces crack.

J

menty666 · #2 2012-01-02, 5:21pm

what glass did you use inside for your implosion?

love2shoot · #3 2012-01-02, 5:24pm

I used some cinnabar redish and a boro yellow still new so i was playing with a couple of scraps

menty666 · #4 2012-01-02, 5:28pm

The giant crack looks like thermal stress, vermiculite isn't really good for solid pieces. If you really need to use it, consider taking a little extra time to make sure the temperature's extraordinarily well equalized by slowly making your way out of the flame, but even then you might run into problems.

love2shoot · #5 2012-01-02, 5:34pm

It just drives me nuts because I've made plenty of 104 pendants and even a marble and they didn't crack befor I got them in the kiln. I thought boro was supposed to resist cracking and allow you more time to work items sorry still a newbie with all this lol

Bunyip · #6 2012-01-02, 5:54pm

Based on your picture, boro shouldn't be cracking like that. I routinely make pieces larger than that and cool them by setting them down ON TOP of a fiber blanket prior to kiln reheating for additional work or annealing.

What your marble looks like to me is what happens when I forget to keep a larger marble warm while working on the backing pattern, and then I blast it with full heat to melt everything in. I get planar cracks at the lens, as the backing has been kept much warmer than the front. Perhaps you're experiencing a similar problem when removing your punties and flame polishing the scar, only you're not adding enough stress to kill it immediately? Make sure you're not a) using tools which suck heat from the glass where you're holding it (ie: cold metal tools, or using a marble mold to hold the completed piece), and b) that you even out the heat in your pieces prior to removing punties, and again after cleaning up punty mark (and in between if it takes you more than 30 seconds or so to do that).

Another possibility is incompatibility in the glass, either due to mixing up rods or COE shift due to overwork (primarily a concern with greens although reducing can cause issues too).

One more thing that someone very wise in the force once told me is that boro likes to be either very hot, or room temperature (cold)....the in-between states are where problems happen.

menty666 · #7 2012-01-02, 6:24pm

I was a little confused too, because I know I've used fiber for some smaller stuff too. Usually, when I see a crack like that it's because I've encased something that doesn't like to be encased, but it doesn't always go all the way through the marble like this did, often it won't even make it to the surface.

Signguy · #8 2012-01-02, 6:54pm

I get the same thing using annealing beads (which are way better then vermiculite). Cracks all the way through on boro unless very small.

drew1492 · #9 2012-01-02, 10:46pm

Some collors are worse than others. I have a purple I will not even try to use in a situation like that knowing it will probably crack, and another purple that gives me no issues at all.

deb tarry · #10 2012-01-03, 9:28am

When most people switch from soft glass to boro they don't realize the extra heat that is required to sink into the piece. When working with soft glass you twirl it in the flame for 10 seconds or so and you know the piece is hot all the way through with boro its longer. The heat can sit on the surface but unless you keep it in the flame and let the heat get deeper the centre will not get it. You might be able to see this by taking a bit of black and putting it in the centre of a clear gather (marble) and as you are shaping keep an eye on the black in the middle if it doesn't turn its red glow the heat is not getting in deep. Doing this exercise will give you a sense of timing in how much time in the flame the piece needs for the heat to "get in there".
As far as reheating a piece in the flame for repair its pretty hard to do that without preheating the piece in the kiln. The kiln can bring the piece up to temperature slow enough that it won't shatter along the fractures that are in the glass. If you can see one crack there is probably more that you can't see and the sudden change in temp from the torch will make it shatter.
I know running a kiln cost a few dollars a day but I advise everyone to have it running and start putting your pieces into it from the torch. Get rid of the fiber blanket. I just hate working on a piece just to have it crack in the blanket cause it cooled down to fast or didn't get the proper heat. I know lots of people that "bench cool" pieces but as stated above its tricky.
Hope this helps and ask more questions if any of the points aren't clear.

Baywinger · #11 2012-01-03, 9:53am

I also find that if you are working in your garage during winter, Boro will shock crack much easier because of the cold air. Pieces that I can bench cool on a fiber blanket the rest of the year crack in the winter, so I find that everything must go directly to the kiln.

Bunyip · #12 2012-01-03, 9:57am

I occasionally bench cool smaller pieces/elements, whether due to absent mindedness or whatever but it's important to kiln soak prior to re-heating unless you like cracks.... It's usually a matter of convenience (or distraction), which (usually) doesn't bite me on the ass - but I certainly don't advise it for someone who isn't sure about the parameters.

My biggest killer is when I spend too much time decorating a larger piece and I forget to keep a good base heat on it - and then I forget to garage it so the heat can even out...then POW. Damn it. I'm learning

Baywinger · #13 2012-01-03, 9:59am

Quote:

Originally Posted by Bunyip

.

My biggest killer is when I spend too much time decorating a larger piece and I forget to keep a good base heat on it - and then I forget to garage it so the heat can even out...then POW. Damn it. I'm learning

Been there myself lol

BellaBean · #14 2012-01-03, 12:33pm

I've had a few crack like that when I was doing detailed implosions and somehow got an oblong air bubble trapped near an edge.

love2shoot · #15 2012-01-04, 12:26am

thanks all for all the information. I guess im just gonna have to leave the boro alone till i know my kiln is available. I am in a shed so the temp with heater is around 70. I may have not heated through. Not sure lol only been lamping for 40 days or so.... lol
One last question. Can Boro be annealed with soft glass??
Thank you J

Firebrand Beads · #16 2012-01-04, 12:36am

short answer is no...

Alaska · #17 2012-01-04, 2:10am

Quote:

Originally Posted by love2shoot

One last question. Can Boro be annealed with soft glass??

See for more discussion....

http://www.lampworketc.com/forums/sh...d.php?t=213941

Bunyip · #18 2012-01-04, 5:49am

In our home studio, Kara works only soft glass, and I'm pretty much boro only. When we work together, we set the kiln for soft glass and we both share the kiln. Once the cycle is complete, I just leave the boro in the kiln until my next solo session, or run a batch anneal program when it's convenient. As we anneal our soft glass at 970 (your kiln may vary!), and boro's strain point is around 950, at least SOME strain relief happens in the boro.

So I would say you can do it...kinda, but run a boro cycle afterward just in case.

I guess that's why the short answer is "no" (LOL!)

Juln · #19 2012-01-04, 12:37pm

Certain kilns aren't planned the best and have heat gradients which can make it work. For instance, in my AIM 99 the front 4 inches are about 950 when the kiln is set to 1050. That's not the most ideal set up but it can work to anneal soft glass and boro in the same kiln.