Glass viscosity and folded and chopped Pelts

[J_Ding]

(I am starting a new thread on this controversial topic that was mentioned in a current thread on cold rolls and other marble artifacts.  Please, no flame wars.  I'm trying to use facts and evidence to address this issue in a different way, and discuss some things.  I'm not going after the 'Miller' machine argument much here.)

I don't mean to open a can of worms on folded and chopped up NLRs--a lot of blood has been spilled arguing that this is just an accidental variant in production--some of those might be artifacts.  BUT, I seem to see those on rebels, superboys, and supermen a good deal, especially on those that seem to have richer glass (I know this is subjective...so don't yell at me).  AND I do see these on feathering two seam slags all the time, which were the same machines that they used to start making NLR's I assume.  National Onyx and then opaque NLR's started both showing up on wholesale documents around 1930...they were starting to move to opaque marbles, as has been noted, because they were cheaper to produce.  On a listing from 1930 for example, those onyx and prima agates were up to 3-5 times more expensive per thousand than the new line (and by experience, I also find slags to be much much more durable)! THAT is a significant difference in the cost of production! Those marbles, the slags and cerise and primas, were much more expensive to produce, and chemically, not the same marble at all, apparently.  And here, I think that the earliest NLRs were still a better marble than they become as we moved to the depression. I think that many of the earliest NLR's tended to fold more, like they did in their slag line, which by that time were being phased out. I do not know of a specific date that would fix when Pelt shifted to cullet...maybe someone can clarify that for me.  I assume here, that the slags were not cullet glass. Later cullet Rainbos fold at a much lower rate, as a random sample of them.

But it turns out, that the feathering slags disproportionately are folded!  I looked at 23 Pelt feathered slags to see which were folded and which were not (and eliminated those I couldn't make out the seams..most those were folded too).  What I did was to measure the mid-point of each seam, and measure their distance from each other, and divided that by the diameter to get a measure, a ratio of the diameter of the marble and the position of the seams relative to each other.  A value of 1.0 would mean, like in rainbos, the seams are 180 degrees opposite of each other.  As the number goes down, the seams are positioned closer together.  For example, in the Cub Scout in the second picture, that ratio, nearly perpendicular to each other, would be just about 0.50.  The closest ones, in which the seams virtually touch each other, the number would be close to zero.  I selected 23 pelt slags of different sizes that could be measured from the nearest mid-point of the seam, and this is what found:  The numbers ranged from 0.30 (very close to each other) to a high of 1.0 (opposite).  Only three of the 23 were anywhere near 1.0 (above 0.90), the remainder where ALL below 0.70, and all but one were below that number.  The mean for all 23 was 0.55, nearly perpendicular to each other, as in the Cub Scout below, and when I eliminated the three, the average fell to 0.49.  This is a random sample in all those I could measure (ok, I have a few more, but they are in a box somewhere).  But when I look at Rainbos, for example sunsets and opaques, finding folded and chopped ones is very very hard to do, and are very much lower in number as in a proportion of them. And twisted NLRs are not even at that level for the most part (less Rebels, Super-whatevers, Liberties, M&K, some Wasps and Tigers  and some Zebras--also many MCS, especially ying-yangs are a bit higher in number than MCR's which tend not to twist).  So what might be going on here?

If you've been around enough on boards, we've seen endless discussions about the Miller rollers, and speculation that these folded NLRs are just outliers, or it has something to do with the feeder mechanism, or even the height at which the molten glass falls before hitting the rollers, which I recognize do happen. Some think they might be earlier.  I know none of those things about marble machines....I haven't even seen one in person...my area is not marble machines and rollers.  But I do have some professional understanding of chemistry and intermolecular forces and physics. I suggest, in the light of the fact that very many Pelt slags are folded, perhaps it is time to ask whether the glass composition has something to do with what tends to happen when the molten glass is rounded and cools, or the temperature of the melted glass. Why are there so very many slags that are folded, but fewer NLR's, and even fewer Pelts in the Rainbo line (they do occur, but not that often, and I'd bet those formula are also different)?  Even though I've been dismissed before in some posts, I bothered to study it a bit further and discovered that viscosity varies considerably in different glass formula...viscosity is technically a measure of resistance to flow in a liquid or molten state...maple syrup and oil for example, are very viscous, water and alcohol less so...that that tends to influence a variety of properties. Viscosity in molten glass is measured (this is a simplification) by torque, rotational force around an axis...and there are devices that will measure these properties. Glass composition and even temperature seems to influence viscosity in glass. It might be time to give glass composition its due, especially as it relates to the problem of chopped up and swirly NLRs and how in some swirls, notably and famously in CAC, tend to produce flames and other amazing patterns in glass.  Is it just coincidence that some CAC swirls are not known to flame, and some are?  And why are those 'some' very often powder blue based, just like in supermen and other light blue based CAC marbles?  I wonder, is it partly in the glass?   I'll accept that a bunch of factors are at play, but I think glass composition needs to be considered also..as influencing how these marbles round up as they cool.  Given that viscosity varies in molten glass, I don't even think that we could discount the effect viscosity has when they hit the rollers, or even their rate of turning, might play a role in how they round into a sphere....but on the Miller machine bit, I'm not going to say a thing! 

Here are a few folded Pelts, a Cub Scout shooter, a big folded superman, and a boulder Rainbo that is folded, and that one too, glows very bright green and the red glass is very clean and deeply saturated.  Coincidence, or are these a bit older?  I think, and I might get flamed for saying so, but I think they probably are older. Can't prove it, but I think they represent the earlier NLR line. All my other Cub Scouts have less color, the ribbons are narrower, and none are folded (but I don't have 23 of them!).  I guess I'm now leaning to some of those fantastic swirly Pelts are 'older', whatever that means.  

[Alan]

Is there a question in there somewhere?

 

[skoronesa]

I think the gist of it is he thinks the fold may be partially due to the design of the machines but that the extent to which it occurs is dependent on the viscosity of the glass. Implying that the fold is not necessarily intentional. 

This is the first I have heard of there being a disagreement on this, nor have I ever thought much of it. I would think for a marble to have a fold instead of having two "pontils" that it wouldn't just drop straight down in the middle of the rollers but rather land off center so it hits one roller and slides to the middle causing it to fold. I have seen some machines, mostly in new jabo videos, the molten glass dripping from the bottom of the pot is cut by a sliding plate. If you positioned the hole centered on the rollers the globs would land off center from being pushed sideways by the shear as it cut them. Maybe someone realized this at other companies and so offset the rollers. The viscosity would still affect the degree to which this occurred as thinner glass would cut easier and not be pushed sideways as much in the process and thus land more torwards center and presumably folding less.

[slagmarble]

In my experience pelt slags seldom have opposite or even neat seams like Christensen's do.  Not unusual at all to find a second seam 90 degrees from the first or in other unusual orientations. 

[budwas]

I feel viscosity due to temperature  would change everything.  The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal concept of "thickness"; for example, honey has a much higher viscosity than water. 

Assuming the shear always ran at the same speed, if the stream had a high viscosity then the gobs being cut would be short and fat where a low viscosity would produce long skinny gobs more prone to folding.

Just my opinion.

Bud

[J_Ding]

2 hours ago, slagmarble said:

In my experience pelt slags seldom have opposite or even neat seams like Christensen's do.  Not unusual at all to find a second seam 90 degrees from the first or in other unusual orientations. 

 That's what I see here too.  Many of them were at 90 degree or so, sometimes often touching.  I see some 90 degrees in CAC two seam slags too, but there the line is usually straighter and more visible.  I've not seen too many German slags, but most of those I think are those, are opposite.

[J_Ding]

36 minutes ago, budwas said:

I feel viscosity due to temperature  would change everything.  The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal concept of "thickness"; for example, honey has a much higher viscosity than water. 

Assuming the shear always ran at the same speed, if the stream had a high viscosity then the gobs being cut would be short and fat where a low viscosity would produce long skinny gobs more prone to folding.

Just my opinion.

Bud

Bud...That was what I've been thinking too. Resistance to flow would be another way of looking at viscosity.  I would expect that CAC flames are long and skinny, as you say. Thanks for the comment! John

[slagmarble]

German slags closely resemble CA with even the lower quality ones generally having good readily apparent seams that are closely opposite each other.