Dichroic Glass, Silver Clay,Fusing Supplies, PMC Classes, Fusing Classes, How to Projects

 

 

 

 

Home
Specials
Dichroic Glass
Art Glass
Fusing Supplies
Fusible Glass Bails
Jewelry Findings
Molds
Kilns
Classes
PROJECTS
FAQ
Product Index
Gift Certificates
What Folks Say!

 

Silver Stain, PMC and Art Glass

Silver stain is the black mark  left on the ceramic kiln shelf (not ceramic fiber) when you fire silver (sterling & fine silver) on the shelf.  Even if you don’t see it later it is still present; even after scraping and re-kilnwashing. 

The purpose of this test is multi-fold:

1] To determine which colors of art glass react with silver so that we can avoid this ugly occurrence when using art glass with PMC.

2] To educate the public so they know why they get these marks on the back of their fused pieces from time to time.

3] To determine if Crystal Clear (1401) is necessary for use with PMC vs. Regular Clear (1101). Crystal clear is more expensive and adds a level of complexity in logistics to the glass studio but not necessarily to the PMC studio.  If you use ONLY crystal clear then there is no problem.

4] To provide data to Bullseye.

Testing process: Small squares of art glass were placed on a kiln shelf that contains silver stain and fired to full fuse. Each square was placed on a silver stain mark.

Clear 1101 No Reaction
Crystal Clear 1401 No Reaction
Deep Royal Blue 1114 No Reaction
Turquoise 1116 No Reaction
Aqua 1108 No Reaction
Erbium Pink 1821 No Reaction
Neo Lavender 1442 No Reaction
Spring Green 1426 No Reaction
Black 0100 No Reaction
Orange 1125 Reacted. Black Mark
Yellow 1120 Reacted. Gets cloudy, had reddish black mark.
Cranberry 1311 Reacted. Black mark.
Sunset Coral 1305 Reacted. Slight discoloration
Violet Striker 1234 Reacted. Yellowish white mark.
Adventurine Green 1112 Reacts very badly. Yellowish white mark
Medium Amber 1137 Reacts very badly. Brown stain w/ yellowish stain in middle.
Chartreuse 1126 Reacts. Yellowish white stain

There are  more colors available but these are the ones we use and sell most often so I started with those.  Note that the regular clear DID NOT react.  This has been my belief all along.  It may be that WHEN a reaction occurs the creator thinks it’s because of the regular clear but it, in fact, is because of some other material present…. for instance….. one of the metals in the dichroic coating, one of the other colors of art glass present, perhaps the clear is spectrum or Uroboros …. Etc….  My own experience with embedding fused glass in PMC has been that clear 1101 does not react.

I will continue to test all the other colors of art glass I have and will also test with squares of dichro to see if any of those react.  I will also test the new Tekta clear from Bullseye. I don’t buy Uroboros clear except that I do have some dichro on it so that will have to suffice as a test. All the art glass is Bullseye. I do have a few colors of Uroboros and I will test those too. I will test the clear 1101 and 1401 again.

When the glass does react it discolors the glass in various ways; this discoloration is not removable even if you grind off the surface. The only efficient way I have found to deal with this in the studio is to use different shelves for silver and pure glass. I cut off a notch from the corner of one group because you CAN’T SEE the stain after you scrap and rewash.

I am sending this document to Bullseye so that they may be able to tell us which chemical(s) are responsible for the reaction and may be able to give us a list of all the colors that contain those chemicals. Perhaps they can also change the formulas so that we can get non-reacting colors.  [SEE BOTTOM OF THIS DOCUMENT FOR MORE TEST RESULTS.]

 Best,

~Nan

top to bottom, left to right:

Sunset Coral, Med. Amber

Chartreuse, Yellow, Adv. Green

Cranberry, Striking Violet

forgot to scan Orange....

 

 MORE.....

Testing Phase #2 - squares with PMC3 Paste & wrapped with PMC3 Clay Coils

TEST #1: Squares of colored art glass, clear art glass, crystal clear art glass and dichroic glass were spotted with PMC3 Paste, dried and fired to 1110 for 30 minutes. 3 Squares were wrapped with PMC3 Clay Coils - 1 Crystal Clear, 1 Clear and 1 Adv. Green which is known to discolor very strongly when fired in contact with silver.

RESULTS: The glass does not change AT ALL at this temperature, i.e. no fusing occurs, no fire polishing, no nothing... the glass just gets hot. 

As you can see in this image, several colors of art glass and dichro have discolored already; yellow art glass and pink/teal dichro(upper left corner) are the most pronounced.  The crystal clear and regular clear have not discolored from the paste OR the coil.  The adv green has started to discolor slightly with both the paste and the coil but it is not so apparent in the image. The dicho that is discoloring has been spotted with paste on the dichroic coated side not on the clear side.  The same colors of art glass that discolored from the silver stain are reacting with the PMC.

 

TEST #1: Squares of colored art glass, clear art glass, crystal clear art glass and dichroic glass were spotted with PMC3 Paste, dried and fired to 1290 for 10 minutes. 3 Squares were wrapped with PMC3 Clay Coils - 1 Crystal Clear, 1 Clear and 1 Adv. Green which is known to discolor very strongly when fired in contact with silver.

RESULTS: The edges of the glass are slightly fire polished at this temperature. As you can see by the images below, several of the pieces reacted to the silver.  The dichroic coating on several of the pieces also reacted.  Much to my surprise BOTH the clear 1101 AND the Crystal Clear 1401 reacted slightly at this temp!!! It's a bit hard to see in the images but it's more apparent in person; there is a slight yellow tinge right around the  paste. The pieces of clear that were wrapped with clay also reacted slightly; they don't appear yellow but if you look at the edges you can see  slight yellowing. The green one reacted A LOT!

Left to Right: Clear w/black streamers, Crystal Clear.

Left to Right: Adv. Green, Crystal Clear, Clear w/black streamers.

Testing Phase #1 - silver stain & sterling wire

TEST #2: The same color squares were placed in the kiln, some on silver stain spots, some on pieces of sterling silver wire. In addition, 5 or more pieces of dichroic glass were place, coating side down, on sterling wire. These were fired to 1110 degrees and held for 30 minutes. This is the lowest firing schedule for PMC3 listed on the sheet that comes with the PMC3.

RESULTS: The glass does not change AT ALL at this temperature, i.e. no fusing occurs, no fire polishing, no nothing... the glass just gets hot.  No silver stain occurred on ANY glass. The Sterling wire discolored slightly and was just beginning to leave a mark on the shelf  but was very faint.

TEST#3: The same color squares were placed back in the kiln, some on silver stain spots, some on pieces of sterling silver wire.  These were fired to 1290 degrees and held for 10 minutes. This is the highest firing schedule for PMC3 listed on the sheet that comes with the PMC3 (although it can be fired higher).

RESULTS: Again, the temperature was not high enough to change the glass in any way.  No discoloration to any glass was present. The silver stain marks that were on the shelf when placed in the kiln are now invisible.

 

 

 

 

Send email to    with questions or comments about this web site.
Copyright © 2002 - 2011 Glass Orchids - UGotGlass? UGotGlass? is a trademark of Glass Orchids.
Page Updated: 11/25/11   Prices subject to change without notice.

 

All images and text are protected by US and International copyright law.