Boro ornaments seem too fragile

[amyhoust]

So I've been making icicle style ornaments in boro. Basically starting with a colour base, encasing in clear, and making a twistie. I've been annealing them with my usual anneal schedule for boro, which seems to make my pieces very strong. But these are VERY breakable.

Now, they are more delicate than anything I have done before, so I don't expect them to be AS strong. But they seem too fragile. Also, I am getting some devitrification on the clear glass (which in itself isn't bad, it almost looks pretty, but it makes me wonder if I'm doing something strange while I'm working the glass).

I'm not completely sure that my anneal schedule is good. Unfortunately I can't remember exactly what it is, its in my kiln which is outside I think it goes up to 1125, soaks for 20 min, then down to 950 for 60 min, then down to 200 at a quite slow rate (150/hr I believe), then off. I may not have this right though, my memory is very fallable! Also I use an AIM kiln with the bead door, so I always seem to need slightly higher anneal temperatures, I suspect that the door lets out some heat. I do anneal my boro fairly high up in the kiln, sitting on top of some little mini plant pots.

But as far as the anneal schedule goes, like I said, other stuff I've done (I guess only ever using just one colour at a time) seems strong. Can using multiple colours in one piece screw things up? I'm still very much a boro noob.

I need help with this soon because I really want to sell these ornaments at my upcoming Christmas shows... I am loving how they are looking but I have broken probably half of them by accident already. If I drop them onto the carpet, they snap! If I drop them onto the table from a foot or two up they break.

Oh and as far as colours go... I think the ones I've been using are mostly glass alchemy... I'm not sure what the clear is. Actually I'm pretty sure it's simax.

And I'm using a minor with two concentrators.

[menty666]

boro anneals at 1050, not 950. 1125 sounds kind of high for a soak, but I have some striking issues of my own, but I think most folks only go up to 1085 or so when they do that.

Other than that....I dunno. I've snapped a couple of mine but they were kind of thin in those spots, so it was my own darn fault.

The devit might be caused by stretching while the glass is too cold, or maybe one of your colors is boiling slightly?

[amyhoust]

I'll double check my soak temperature. I know I started with a schedule that I got from somewhere online, and ended up bumping the strike temp up somewhat. Maybe I didn't bump up the soak temp... (and maybe it actually is at 1050 not 950, I might have remembered that wrong).

I probably am stretching the glass out while it's fairly cool, I didn't know that caused devitrification! I tend to keep stretching/twisting with these as long as I can. Like I said, I'm a newb, I don't have a lot of control yet!

[Kalera]

When you twist boro at too cool a temp, you have to bring it back up to a higher temp or the twisted parts are extremely brittle. Hopefully twisting at a higher temp and/or reheating your piece thoroughly will help.

[Alison D]

Amy,
I asked a question like this last year but didn't word it well so nothing was resolved. I was having the same problem. I think Kalera has nailed the problem. Can't wait to melt glass (hotter).

Great explanation Kalera. That will be an huge help. That might be why my sister broke so many of her icicles last year.


Thanks,
Alison

[Ro]

i agree with it being hotter to twist, if you see any frosty areas, they need to be fire polished.
ro

[earlbacher]

you want the whole thing smooth and as even as possible, crank the heat to the point of almost loosing control of the glass

[Karen Hardy]

I'm going to chime in with a different angle.
Looking at the ornaments you posted, I can see
several that have "ledges" and "cuts" in them.
I'm probably not saying it right - but these are areas
that are not smooth and flowing. They kind of jut into
the piece.

Anytime you have areas like that, the piece will be weaker there.
Sort of like an undercut area - that's where they will snap and
break. The area has to be melted smooth and flat (or tapered) and
can't have any stepped areas. As an example - my pendants kept
breaking at the loop area because I had undercuts there.
When I melted that area into the surrounding area the breaking stopped.

[amyhoust]

Originally Posted by Karen Hardy

I'm going to chime in with a different angle.
Looking at the ornaments you posted, I can see
several that have "ledges" and "cuts" in them.
I'm probably not saying it right - but these are areas
that are not smooth and flowing. They kind of jut into
the piece.

Anytime you have areas like that, the piece will be weaker there.
Sort of like an undercut area - that's where they will snap and
break. The area has to be melted smooth and flat (or tapered) and
can't have any stepped areas. As an example - my pendants kept
breaking at the loop area because I had undercuts there.
When I melted that area into the surrounding area the breaking stopped.
Attachment 71528

While you might be right that the pieces are weak there (and I will definitely keep this in mind!), I just want to point out to others reading this thread that the icicles weren't breaking in those specific places. And they did/do feel very brittle all over. I'm going to try working the glass a bit hotter and see how that does.

[evolvingBeau]

Originally Posted by Kalera

When you twist boro at too cool a temp, you have to bring it back up to a higher temp or the twisted parts are extremely brittle. Hopefully twisting at a higher temp and/or reheating your piece thoroughly will help.

That's definitely what's going on there. Ideally you want to do one big deep heat and then one pull/twist. That's going to give you the least amount of stress to begin with and a nice consistent and smooth twist/taper. The frosty stuff is devitrivication from the glass being moved when it's too cool on the surface.
Alternatively you can kind of heat while you pull, though this isn't really a good habit but is sometimes just what you have to do if the heatbase of the glass fades too much...
If you do a nice big heat and need to introduce more heat during the pull, turn up the propane (or lower the O2) for a broader bushier flame, this will heat the whole piece more evenly..
The German glassblower I apprenticed with had me making tons of icicles and as simple as they are conceptually they do take a bit of practice to be consistent with.

[suzanne]

ditto on what kalera said, work hotter. The devit comes from not heating enough, I've had it happen when I first started working with boro. After a nice hot flamebath, the devit dissapeares

[Coffeebean]

agreed. let us know how it goes when you work it hotter

[amyhoust]

They definitely seem way less brittle. Haven't even gotten around to annealing them yet, but yeah, they already seem better.