NS-98 Loch Ness cracking problem

[Fairytalebeads]

Hi there,

I have troubles with NS-98 Loch Ness - I love the color and the sparkle but up to now I do not have a single piece a I did without cracks.

First I tried it deep encased - major failure!
Ok, then I thought it does not like encasing, so I just used it for backing on a marble - cracks all over the surface and especially where it touches the clear.
Well, maybe it was to thick - next try was only a very thin layer of it as the final surface, same result...

Any ideas?
I am using Simax clear btw...

Thanks
Michael

[Cosmo]

Are you reducing the glass as you melt it?

I've used Loch Ness deep inside marbles, on the surface, and everywhere else, and never had a problem with it cracking.

[Fairytalebeads]

Nope, working in an neutral to oxidizing flame.

[Cosmo]

Are you using seconds or anything?

Honestly I haven't bought any Loch Ness in a while. A couple years ago I bought 5 pounds of it and I'm still working through it, so the formula may be slightly different now.

What is your annealing schedule? A lot of sparkle colors don't like to be garaged for long.

[Fairytalebeads]

Hmmm, normally I have the larger marbles soak for 2 hours at 565°C, then strike at 607°C for 20 minutes if needed and then cool down.

What would you define long for garaging?

I will do a quick test today, just encasing some Loch Ness and add some surface dots over clear, no striking or garaging with it. I will post pics tomorrow of the result (altough I know how it would look like already...)

Cheers
Michael

[Cosmo]

How big are the "larger" marbles? How quick are you cooling them down?

[Bunyip]

I've not had much luck with lochness either until got off the concentrators - I was apparently reducing it too much despite using what appeared to be a fairly oxy flame. Even then it was kind of chancy until I started using it to create encased stringers. You can also try mixing it down with clear or a dark transparent for surface work...

First off though it's important to eliminate your kiln as the culprit...Those sparkle colors are notorious for changing COE if they soak at high temperatures for too long - a lot of people like to garage them below the annealing temperature to avoid that.

[Fairytalebeads]

Cosmo, my "larger" marbles are around 45mm (yes I know, that's not too large for some of you guys... )

After anealing/striking I ramp down to 510°C @ 20°C per hour, hold it for 10 minutes. Then I turn the kiln off. I have a Paragon Bluebird XL and it will take around 5 hours to cool down to room temp when turning it off at 510°C - that's ~100°C per hour.

Bunyip, I am working on a GTT Scorpion running on 2 5lpm concentrators. My flame characteristics tells me that I am working with a neutral to oxidizing flame...could that be the problem? Still not enough oxygen? hmmmm

Thanks so far
Michael

[gmkcpa]

A 45mm marble is almost 1 3/4". That is a healthy size. I anneal them at 1050 for 5 full hours, drop down to 960 at 60 degrees/hour, let them sit at 960 for 2 hours and then shut the kiln off and don't open the door until the kiln is under 140 degrees. With this schedule I've made hundreds of marbles with no cracks. HOWEVER, I did do a spiral marble a few years ago using loch ness for the spiral. The marble did not crack, but the loch ness checked uniformly along the whole spiral. It is a beautiful look that I'll probably never be able to duplicate.

[Cosmo]

Originally Posted by Fairytalebeads

Cosmo, my "larger" marbles are around 45mm (yes I know, that's not too large for some of you guys... )

After anealing/striking I ramp down to 510°C @ 20°C per hour, hold it for 10 minutes. Then I turn the kiln off. I have a Paragon Bluebird XL and it will take around 5 hours to cool down to room temp when turning it off at 510°C - that's ~100°C per hour.

Bunyip, I am working on a GTT Scorpion running on 2 5lpm concentrators. My flame characteristics tells me that I am working with a neutral to oxidizing flame...could that be the problem? Still not enough oxygen? hmmmm

Thanks so far
Michael

A Scorpion on 2 5LPM concentrators? I think that may be your problem. I can't imagine working a marble that size with so little flame. With concentrators, what looks like a neutral flame is actually reducing. The purity of oxygen coming from concentrators isn't as pure as tanked oxygen. And, I imagine that running them wide open like you'd need to to get a good flame on that torch the purity has to suffer even more.

[Fairytalebeads]

Originally Posted by Bunyip

I've not had much luck with lochness either until got off the concentrators - I was apparently reducing it too much despite using what appeared to be a fairly oxy flame. Even then it was kind of chancy until I started using it to create encased stringers. You can also try mixing it down with clear or a dark transparent for surface work...

First off though it's important to eliminate your kiln as the culprit...Those sparkle colors are notorious for changing COE if they soak at high temperatures for too long - a lot of people like to garage them below the annealing temperature to avoid that.

Chris, thank your for the hint - I will make another try with an encased Loch Ness stringer where I try to work with a "super oxidizing" flame set while encasing - at least as much I can get from my concentrators.

Originally Posted by gmkcpa

HOWEVER, I did do a spiral marble a few years ago using loch ness for the spiral. The marble did not crack, but the loch ness checked uniformly along the whole spiral. It is a beautiful look that I'll probably never be able to duplicate.

Gerald, that's the same effect I had some time with a vortex marble where I had 4 stripes of Loch Ness - The clear touching the Loch Ness had tiny cracks all over it - very interesting look, the marble did not crack though.

Originally Posted by Cosmo

A Scorpion on 2 5LPM concentrators? I think that may be your problem. I can't imagine working a marble that size with so little flame. With concentrators, what looks like a neutral flame is actually reducing. The purity of oxygen coming from concentrators isn't as pure as tanked oxygen. And, I imagine that running them wide open like you'd need to to get a good flame on that torch the purity has to suffer even more.

Cosmo, after thinking about that the last hours, I have the bad feeling that you are absolutely right.
Although this two concentrators are "almost" brand new (4000 hours), and I am running them still in their "green" area. I do not have a O2 measurment device, but when I trust the display on the devices, I am running at around 10 LPM 90% O2.... (at around 600 mBar / 8 PSI O2 preasure)

Cheers
Michael

[Bunyip]

Remember - oxy concentrations get higher as you lower the output from the concentrator.

If I'd known THEN what I know NOW, I would have rigged up the 150 CF cylinder I have so I could use it when I needed to. There's nothing like tanked (or liquid) when your flame needs some AUTHORITY (or just needs to be pure oxy!) That being said, don't get discouraged, you can do almost everything with your setup, provided you can accept that certain colors aren't going to cooperate, and that you're going to have size limitations - particularly with solid work.

Good luck!

[Fairytalebeads]

Thanks for you help!

Cosmo, I guess you found exactly my problem! Not enough O2!

Here is a pic of a quick pendant using encased Loch Ness (encased with as much O2 as possible) and then worked "normal" into the pendant. Result: no cracking at all.



I will try more "solid" Loch Ness into a piece later that week.

Cheers,
Michael

[joebirder]

I was going to say the O2 was the problem too... I have no ploblem when it is kept highly oxegenated.. When I don't I get fractures every time..

[Otter's Flame]

Super oxidizing flame.

[Jaterwunky]

Chris,
question for ya... I have both tanked and concentrators... My problem is I can't rig up to switch... Ie I have to disconnect frrom oxycons and then reconnect to tank or backwards.... The only y connector I can find is one way valve unfortunately it goes wrong way and don't want to damage my sieves in my concentrators.... Anybody have a system for this. Tight now I only have a lynx so no footpedal although I am wondering if I jury rig a foopedal for my lynx... Can it be done anyone????
My problem of the day.....

Originally Posted by Bunyip

Remember - oxy concentrations get higher as you lower the output from the concentrator.

If I'd known THEN what I know NOW, I would have rigged up the 150 CF cylinder I have so I could use it when I needed to. There's nothing like tanked (or liquid) when your flame needs some AUTHORITY (or just needs to be pure oxy!) That being said, don't get discouraged, you can do almost everything with your setup, provided you can accept that certain colors aren't going to cooperate, and that you're going to have size limitations - particularly with solid work.

Good luck!

[Bunyip]

Deb, I'd probably have used a brass Y connector, with a shutoff valve positioned so that oxy from the tank couldn't backflow to the oxycon...making sure that the oxycon was OFF before closing the valve...



Please, consult with someone who is more knowledgeable than I before trying my jury-rigged and no-doubt doomed-to-ignominious-failure idea...