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Tips, Techniques, and Questions -- Technical questions or tips

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Old 2014-05-30, 1:07pm
EJohnsonArtGlass's Avatar
EJohnsonArtGlass EJohnsonArtGlass is offline
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Join Date: Sep 30, 2008
Location: Boulder, Colorado
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Post How to work Mother of Pearl or Satin Glass

Remember these little Czech Mother of Pearl beads from the bead stores? They were always my favorites. For awhile in the 1990s and early 2000s it was possible to get this glass in the US, so it made its way into people's stashes. If you get some, here's how to work with it.

Most of the glass you see above is Czech, bought from C&R Loo between 2000 and 2002. I have no idea when it was actually made. It was labeled as 104 compatible and I’ve done pull tests with Moretti black, white and clear to confirm. The compatibility seems good to me. The colors are beautiful jewel tones filled with fine shimmery sparkles. They would make terrific base beads or look good as stripes over other colors. The effect would probably not have much impact for stringer decoration.

This type of MOP was made by alternating layers of transparent color and opaque mother-of-pearl on the gather, then pulling out into canes (relatively thin) or rods (thick). You can see the bullseye pattern on the cane and rod ends. At one time I thought to “improve” this glass by melting it to liquid in the flame and mixing it up, with the idea of dispersing the glittery parts more evenly. But overheating the glass to yellow hot just destroys the sparkle. This glass is best used cool, though getting it orange hot doesn’t seem to harm it any. It likes a cool oxygen-rich flame.

Depending on the color the glass can be in a huge variety of diameters. Some colors came in 4mm to 14mm canes from the factory (most around 8-10mm), others in rods from 19mm up to 26mm (one inch) thick. Don’t be scared of the thick rods!! I’ve actually come to like them better than the thinner lampwork-ready canes!! I find that after I pull them down they have a nicer sparkle pattern than the smaller canes. And the colors are definitely worth the trouble. At the end of this post I've shown pictures and instructions for how to pull down the thick rods.

Below are pictures of the individual colors. They may be helpful to you in deciding what to buy if you have the chance. At the bottom of this post there is information on how to pull the big rods down into thinner canes. You need a torch at least the size of a Minor burner, and a kiln.

I’m sorry the pictures don’t really show the glitter of the MOP. I can’t seem to get the camera to pick it up on the white beads,
although it shows a bit better on the gray. These rods were all of reasonable lampworking size to begin with:
104 Mother Of Pearl Bright White cane, 4mm-10mm in diameter,
104 Mother Of Pearl Warm White cane, 8mm-10mm in diameter
104 Mother Of Pearl Medium Gray cane, 9mm-10mm in diameter

I didn't find much difference in color between the Bright White and Warm White, although the canes of the Warm White were thicker.

104 Mother Of Pearl Pale Pink, large rods about 1" diameter
104 Mother Of Pearl Cranberry Pink, large rods about 1" diameter
I had two different-appearing rods of cranberry pink, but they both worked out to about the same color when used.

104 Mother Of Pearl Gold/ Light Amber, large rods about 1" diameter
104 Mother Of Pearl Leaf Green, large rods about 1" diameter
I found that my particular gold rods had a bit less sparkle than the other colors.

104 Mother Of Pearl Lilac (Lavender) large rods about 1" diameter
104 Mother Of Pearl Violet, large rods about 1" diameter
When I sold these the lavender was less popular but I don't know why. The color is pretty and it has loads of sparkle.

The blue glass pictured below is French, but I’m embarrassed to say I can no longer remember the name of the company that made it. Around 2005, while I was the purchasing agent for Glasscraft, I bought glass from an old factory in Massachusetts. Most of the glass had been made in France in the 1950s and imported to this factory where it was used to make buttons. Some was as old as the early 1900s! The button process stopped in the 60s and the glass had been moldering in the factory basement for 40 years, where the wooden crates had rotted around it. I spent many hours washing that glass so it could be sold! This was the source of the beautiful lead crystal “Green Moonstone” glass that’s so hard to find anymore.

The blue antique Satin Glass was made in 1920 and 1921 – almost a hundred years old!

This glass was labeled as “satin glass” and does not have Bullseye pattern on the rod ends like the Czech MOP. Whatever makes the MOP effect (zillions of tiny bubbles, perhaps??) is already dispersed throughout the glass. Both the light and medium blue are good expansion matches for the System 96 colors I tested them with. Again, there are no guarantees. I have no idea if these colors contain any lead.

I have some in a warm light lavender-blue and a cooler medium blue. The rods are mostly between 10mm and 12mm thickness, though there are a couple as thin as 8mm and some as thick as 14mm ones thrown in. Even the thickest rods don’t seem to be very shocky. Certainly they are less shocky than most of the Devardi glass I have used.

The Satin Glass was made for use with an alcohol lamp and forced air from a bellows such as the Blashkas would have used. It was meant to be warmed (think putty, not honey) in a soft, cool flame and then pressed in brass presses.

The outside tends to fizz and bubble in the flame. I think this is because the zillions of tiny bubbles along the surface of the glass break as you heat it. I've discovered that if I go in close and hot for just a few seconds (slide back and forth, keep the rod turning) I can melt a thin skin on the glass surface and pop all the bubbles so that it smooths out. Then I back away and work cooler, so the center of the rod gets warm, but not liquid.

You must work slowly and be patient as you would with an alabastro. Wait for slow heat to soften the glass, shape with brass tools or presses, and let slow heat smooth out any chill marks your bead's surface. Graphite seems to leave a scum on the surface for me, but maybe my graphite tools just need cleaning.

If you get the Satin Glass light orange hot and use heat alone to shape it into a sphere a la Jim Smircich, you'll lose the sparkle, although the medium blue is still a gorgeous transparent color. The beautiful shimmer is worth the wait. The glass will make gorgeous base or pressed beads.

When you're trying to heat the end of a really thick (10-12mm) cane and you're making a small bead, it seems too big and clunky to work with. You're tempted to get it liquid so you can stick it to the mandrel and drip it on like honey. Don't! Instead, on-the-fly you can warm and inch or two of the end and stretch it down bit thinner, maybe 5 or 6mm. Then heat the new thinner end to apply to your bead. Medium orange hot will not hurt the sparkle, but yellow hot will destroy it.

If it's easier you can just cut the thick canes into 2" long chunks with your nippers and pull them down ahead of time like you would the big rods, using the instructions below.

96 Antique French Light Periwinkle Blue Satin Glass canes, 11mm-15mm diameter
96 Antique French Medium Blue Satin Glass canes, 10mm-12mm diameter.

I’m sorry, no amount of fiddling has been able to get the colors of this glass correct in the pictures. Must be my lighting that’s making these look too green.

The light blue glass is actually a light periwinkle blue. The color of the swatch below the rods isn’t exact either but it’s much closer to the color of the actual rods. The sparkle is less dense than the Medium Blue. Preheating the rods as you would for Devardi glass makes everything go faster.

Same photo difficulty with the Medium Blue satin glass. The color is less green than what you see here, but doesn’t match anything at all in my glass collection! It falls somewhere between sapphire blue and capri blue. The swatch is not an exact match but much closer than the photo. The sparkle is dense and beautiful.

Here’s the “quick and dirty” way to pull the thick rods down into cane. It will take about 5 minutes to pull down each chunk.
Using a hammer, a tile nipper or diamond saw, break the rod into chunks of about 1 ounce. One ounce is a cylinder about 1” diameter and 1" high, and will pull down into a cane that’s 6mm thick and 13” long. It's easiest to use a saw if you have access to one. The saw-cut ends melt out smooth and clean and do not have to be “peeled” off. But if you have to break the glass up with a chisel and hammer that's okay. Weird shapes, chips or triangular pieces also work just fine. The shape is not important.

Toss into a kiln and heat at full speed to at least 1025F. In my SC-2 kiln I can go up as high as 1050 before this glass starts to get tacky on the surface. Use the highest temp you can get away with before the glass actually starts to pick up texture (and possibly dust) from the bottom of your kiln. This will reduce the time it takes to pull the chunks out even further.

After preheating at full temp for at least 30 minutes (to get the chunks hot all the way to their centers) melt the end of punty rod and use it to pick up one of the chunks from the kiln. I use 6” Moretti transparent rods because they are the same coe, so you can leave them attached as handles and use the MOP down all the way to the very last bit. It works best to attach the punty to the edge on one side of the chunk. Attach a second punty rod onto the opposite edge of the chunk and dive into a neutral-to-oxidizing flame. Don't worry about thermal shock and explosions! The glass is already well above annealing temp. There’s no need to waste time making “caps” of clear for pulling out the chunk as you would to pull a murrini cane, because there’s no need to maintain the shape or the color pattern inside. This is a very quick and dirty process.

If the edges start picking up a glowing orange scum you are reducing the glass - add oxygen or move back from the torch face. Using a flame the size of my forefinger, such as you’d have on a Minor Burner, you can soften the chunk to dark orange color in about 5 minutes. If you have a bigger torch you can start with bigger chunks and pull them into longer canes just as quickly. There’s no need to worry about whether the cane you pull is even in thickness – an ugly uneven cane makes beads just as pretty as one that looks machine made.

You want the glass to be stretchy, not runny, so don’t try to get it into a completely melted “football” shape. While your chunk still has a little dimension left but is warm in the center and can be stretched, pull it out to pencil thickness while TWISTING A LITTLE. You can see from the pictures that my canes are not smooth – the glass was stiff enough to leave a texture when twisted. The twist gives a nice even dispersion of the mother of pearl throughout the cane without losing any of the sparkle. A cane pulled down from the thick rods by hand and twisted this way actually makes a prettier mother of pearl pattern in a bead than a 6mm MOP rod from the factory.

The new thinner canes can be used as-is, but if your kiln is big enough to hold them it's a great idea to run them through an annealing cycle before using. That way you remove cooling stress so they're less inclined to thermal shock when in use.

Have fun!

Last edited by EJohnsonArtGlass; 2014-06-05 at 7:00pm.
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Old 2014-05-31, 7:06am
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PaulaD PaulaD is offline
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Excellent article. The glass is gorgeous! Thanks!

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Old 2014-05-31, 6:40pm
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flaming_fools flaming_fools is offline
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Hope they still have someat CR Loo - go there about 2x a year as they are only about 20 miles away. I have never noticed it there.

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Old 2014-05-31, 9:19pm
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Binks Binks is offline
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Posts like this are one of the reasons I love this forum!

Thank you so much for sharing this info.

I don't have any of these glasses, but I'm so enthralled reading about them!
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cane, czech, french, how to, mother of pearl, pull down, rod, satin glass, stretch, tutorial

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