Knobs Cracking, Brain Exploding

[Rebekah]

I just learned in the last few days that every knob that I'm making is cracking in the exact same place, every time. I didn't know until I started making ones that weren't opaque. My kiln schedule is very conservative, I'm putting them in the kiln warm, I'm warming the insert before it goes into the kiln. Where you see the cracks, there is an indention in the insert.

http://images.delphiglass.com/image_new/203953.jpg

Here are the cracks:

171308

You can see that the cracks start at those indentions. What can I do? I'm completely freaking out here. I've closed my Etsy store until I can find a solution.

Any ideas?

[LyndaJ]

I was reading about this either in the back pages of the boro room (I think here), or on GLDG. They said it's best just to use a large mandrel, clean it out part way and glue in the piece. Kalera had posted her solution in it.

Here it is
http://lampworketc.com/forums/showthread.php?t=42591&highlight=drawer

[menty666]

I know with boro, you can't just wind the glass on because it's not compatible.

I'd be willing to bet you're having a similar situation here with the soft glass where it's contracting at a different rate. Even if the metal to glass connection wasn't bad, it's possible the insert's expanding inward like a battering ram, then when it pulls back, crack.

Are they the same kind of steel as the mandrels?

[GinnyHampton]

Is it really a crack or a bubble . . . . it's hard to tell from your picture. I wonder if the indentation in the insert is causing you to create a bubble in your glass . . . when you lay your glass on, maybe the glass isn't getting INTO the indentation and makes a bubble ring.

Could you take a thick stringer using your base color, fill in the indentation (push glass into that space) and then proceed with your knob as usual (??)

[menty666]

I was reading about this either in the back pages of the boro room (I think here), or on GLDG. They said it's best just to use a large mandrel, clean it out part way and glue in the piece. Kalera had posted her solution in it.

Here it is
http://lampworketc.com/forums/showthread.php?t=42591&highlight=drawer

That's the way I make mine too.

EDIT...NOT the way I make mine, but that's pretty darn clever :)

I make mine on the end of a 5/8" steel rod dipped in bead release. I mark how the length of the insert on the rod, then wind the glass from there to the tip and over then start building up my knob itself. The mandrel and knob go into the kiln through the doggy door, then I pull it out, give it a clean, and epoxy in a brass insert.

[ChaseDesigns]

OKay, I am wondering if you can coat the insert with bead release part way up, if that will solve your issue.

It looks like it is happening near the bottom right?

And while having bead release on the insert wouldn't be pretty with transparent, I don't think glue woudld be either. Just a thought.

This really really sucks. I am so sorry Bek. :(

[ChaseDesigns]

Or are the cracks where both indentations are?

[Marcy]

Bek, what is your kiln schedule? What are you holding at? Could you increase the temperature and hold at a higher heat for a longer period? i don't know the answer to your question, but it's worth a try.

Marcy

[JavaGirlBT]

Rebekah I'm so sorry they're cracking. The only time I've had a problem with cracking was using effetre intense blue transparent, which seemed to be a tiny bit incompatible with the steel as well as with the opaque blue glass I used. But then I've only used the Marj Bates inserts for knobs, which are smooth - no indents. Maybe the indents are causing an uneven cooling and the cracking? Are your opaque knobs cracking there too or can you not tell?

[ChaseDesigns]

Here is another thread:
http://www.lampworketc.com/forums/showthread.php?t=130227


and Ellen says this:
Which transparents? I found that effetre dark intense blue did that to me. I've used other transparents such as cobalt with no problems.

Also, you have to be sure to keep the stem area nice and warm while you're making it because superheating it right before you put it in the kiln may not be enough to heal any cracks that develop while you're making the knob.

[ChaseDesigns]

Rebekah I'm so sorry they're cracking. The only time I've had a problem with cracking was using effetre intense blue transparent, which seemed to be a tiny bit incompatible with the steel as well as with the opaque blue glass I used. But then I've only used the Marj Bates inserts for knobs, which are smooth - no indents. Maybe the indents are causing an uneven cooling and the cracking? Are your opaque knobs cracking there too or can you not tell?

I think you are right about the indents. That's where she said they all are cracking.

And there you are Ellen. :wave:

[ChaseDesigns]

Marcy, we gave her a real conservative annealing schedule last night, so I don't think that is it.

[JavaGirlBT]

Another thing, all the knobs I've ever made are thin around most of the length of the insert, as opposed to your design. I don't know if that would make a difference. Too much glass around the insert? Is that possible? Maybe if there's a tiny bit of incompatibility between the glass and the insert, the bulk of the glass being there magnifies the incompatibility?

I'm just throwing out ideas here.

I got cracks like that when I used intense blue trans around the stem of the knob, so I started making the knobs out of opaque blue around the stem and intense blue trans for the ball of the knob. I also wound up with cracks like that where the opaque met the transparent. So i had to redo all my knobs in only the opaque blue.

Transparents are slightly stiffer than opaques, so could certain transparents be just a tad more incompatible?

Next time I can, I'll make a knob like yours and see what happens. What color did you use?

[Nicker]

Bek I make gear shifts out of 104 which are similar in size to your knobs. Actually they are bigger. I wind them right onto the nut and anneal at my regular schedule. I've made dozens over the last two years and had no cracks. I am wondering if you have a in compatible color?

[Gelly]

Oh no!! :sad: I'm sorry Bek, all that beautiful work! Hopefully you are wrong, and it's not all of them.

[Rebekah]

It's all of the colors that I'm using. The white, the aqua, the teal, the orange, the red. I'm going to use bead release and try that. I don't know if the indentions are the problem but they may be.

It's three weeks away from the Gathering so I don't really have time to experiment. I'm going to use bead release for now and epoxy them in but when I get back from that, I'll figure this shiz out. Or I will kill a mofo.

[ChaseDesigns]

I mailed you some bead release today, if you still can't find yours.

[Rebekah]

I'm going to get some over-nighted from Mountain Glass Art. Don't sweat it. I'm just so pissed right now.

[amywashere]

Rebekah: I worked on a large project with glass and metal - it was a wrought iron banister for a staircase - the whole thing was created to look like a giant vine and the customer wanted each leaf filled in with glass rather than spaces. I did much research and tried to convince the wrought iron man into different solutions - the bottom line is that unfortunately the coe of metal and glass are very different. I think your knobs are gorgeous - I am with Janelle on what to do - there are amazing glues out there that would keep that knob on that screwy bit forever. Best of luck, I am sure you will find a solution that works for you. And, in the end with the staircase - the wrought iron man covered the whole thing in varnish and it kept all the pretty cracked glass in place!
Amy

[RSimmons]

I suspect that the edges of the indentations might be creating stress points. I had all sorts of problems with lamp finial inserts, more often than the knob inserts but the same issues. When I do this kind of work now I put bead release on the inserts. After they come out of the kiln I pull the inserts out, clean out the holes and glue the inserts back in. The cracking problems stopped when I started working that way. It's more work but I've been a lot happier with the long term results.

Robert

[Rebekah]

That's what I'm going to do, Robert. If you don't mind my asking, which glue do you use? Is is something specific or a five minute epoxy?

Thank ya'll so much. I appreciate the compliments on my knobs more than you know. I don't usually put my little beads out there but it means a lot to me that ya'll like them. This kind of breaks my heart because I was so excited and had set up my Etsy shop, had awesome friends promote me on their blogs, had a good friend buy two knobs and now I'm stuck with bupkis. I'm going to order some bead release today and the first thing I'm going to do is make Fiona knobs to replace the ones that she purchased!

[GlassGalore]

Thank ya'll so much. I appreciate the compliments on my knobs more than you know. I don't usually put my little beads out there but it means a lot to me that ya'll like them. This kind of breaks my heart because I was so excited and had set up my Etsy shop...(snip)

Just a temporary set back... don't get too discouraged. They are Gorgeous and I was drooling over your Etsy shop last night, trying to decide which colors would look best on which furniture, etc... :)

[Rebekah]

Thank you Lisa, that's really sweet. My bead release will be here on Tuesday (haven't used the stuff in years!) and I just need to get some epoxy and I will be back up and running. It's pretty hard to bring me down but this morning really got to me. Now that I have a plan, I'm feeling better.

[Cosmo]

Try this (I saw it somewhere, but can't remember where)...

Go to the hardware store and buy a bunch of just plain metal nuts that fit the mandrel/screw you are using. Don't get the ones with the rubber insert, obviously. Thread three or four of them onto the end of the mandrel in place of the insert. Thread them right up next to each other. Then make your knob as usual. When you are done the knobs stay in place.

I saw someone else doing it like this and it seemed to work really well for them.

[yamaha200]

I have some inserts that are a bit different style - no indents. I could send you a couple if you'd like to try them and see if you have better luck without the indents.
laura

[LyndaJ]

Triolyse is what I've seen used the most
They have some here http://www.delphiglass.com/index.cfm?page=itemView&itemSYSid=187908

[Michelle Bryant Designs]

Well, hurry up figuring it out, for God's sake. I'm lusting after your knobs!

<mwah hah ha hah haaaaaa>

[GinnyHampton]

I'm lusting after your knobs!


HELLO!
:oops:

[Michelle Bryant Designs]

<SNORT> I showed my husband her Etsy store yesterday, and I'm running around the house saying, "Where can we use those knobs! They're gorgeous!"

:-)

(Sorry, didn't mean to sound that risque!)

[Rebekah]

Awwww, thanks Michelle!!! I'm working on it! I'll be opening the store back up in the next few days and stocking with the same lines of stuff as before...just not cracked. :lol:

[beadsoncypress]

Have you tried the brass inserts? I can send you some (much cheaper too!)

[RSimmons]

[QUOTE=Rebekah;2556165]That's what I'm going to do, Robert. If you don't mind my asking, which glue do you use? Is is something specific or a five minute epoxy? ]

Five minute will do, but the slower curing epoxies have a stronger bond. If you're doing opaques you can also use JB Weld (the slow cure one). It's a 2-part adhesive that's seriously strong, but black/dark grey and looks bad in transparents. I've used it to repair a microscope part here at work that no other adhesive would hold. It's not pretty but it'll hold on like grim death.

Robert