Mosser Cat Glass Types and Finishes
In this section, we will cover the various finishes that Mosser cats come in and the process of how they are made. We will also cover the different types of glass Mosser cats come in, such as Opalescent, milk, and Slag glass. We hope that after reading below, you will feel confident in identifying the many unique finishes and types of glass that Mosser cats come in.
Mosser Cat Glass Finishes
Glossy Finish
For Mosser cats to get a beautiful glossy finish, they have to take a couple of trips through the glazer, a large kiln with flames directed at the glass. The cats are rotated in a circular motion through the glazer. First upside down, and then right side up. As the cat moves through the glazer, intense flames fire the glass and melt off the very outer layer, leaving it with a smoother, shinier finish. This important part of the process is actually polishing the glass. This is the reason your Mosser cat has such a glossy surface.
Carnival Finish
During the manufacturing process, if your Mosser cat is supposed to have an iridized (carnival) finish, it heads over to a separate spraying booth. While the cat is still hot from the glazer, it's sprayed with metallic oxides (sometimes called metallic salts). The metallic salts react to the heat of the glass, which brings out the iridescent properties of the metallic oxides, creating a rainbow iridescence across the surface. Carnival finishes can vary greatly, from traditional rainbow colors to hues of copper, gold, purple, and green. They can have quite a stunning effect.
Satin Finish
Cats that are supposed to have a satin finish are produced by spraying hydrofluoric acid or hydrofluoric acid fumes on the surface. The acid cuts through the uppermost layers of the glass to give it a satin-like look and feel and remove the shine. Certain colors can appear very similar to sea glass, such as the green and blue cats pictured above. Collectors have become quite fond of satin finishes because of this. There are also Mosser cats that have been sandblasted in-house at Rosso Glass to achieve a satin finish. These cats were purchased from Mosser Glass in regular or iridized finishes, and Rosso Glass satinized a percentage of them once they were in their inventory.
Luster Finish
Mosser Glass only made two colors with a luster finish. The color "Opal Luster" (pictured left), and the color "Royal Luster" (pictured right). If you happen to own one, you are very fortunate since they can be quite difficult to find. Luster glass is made by applying a thin layer of a composition that includes metal and metal oxides to a surface and then heating the surface. The metallic oxides can be dissolved in acid and mixed with an oily medium. The luster decoration is created by firing metal oxide stains into the glass. It's a very unique effect and gives the cat a metallic sheen.
Different Types of Glass
Opalescent Glass
Opalescent Mosser cats can have white opalescence on the ears, face, feet, tail, the bottom of the base, and sometimes traces on the body. This type of opalescent glass is produced by re-heating parts of the molten glass when it has just started to cool. Heat-sensitive chemicals in the glass turn the re-heated sections a translucent white. The easiest way to do this is by putting the newly pressed glass back into the furnace entrance, and those parts closest to the heat will turn white. Note: This white effect sits on the surface of the glass, never underneath it. This is how you can tell it apart from slag glass. The amount of opalescence can vary per cat; some have opalescence on the face, while others do not.
Windfrost (Heavy Opalescence)
Mosser Glass made Windfrost cats in the following colors: Crystal Windfrost, Blue Windfrost, Green Windfrost, and Pink Windfrost (which looks like orangish peach). The process used to make these cats is the same as the opalescent cats above. The difference is that these cats have extremely heavy patches of white opalescence all over their bodies, which means they were re-heated for longer periods to achieve this effect. Interestingly enough, the ear tips on Windfrost cats seem to be clear, unlike their regular opalescent counterparts. This type of opalescent glass is produced by re-heating parts of the molten glass when it has just started to cool. Heat-sensitive chemicals in the glass turn the re-heated sections white. The easiest way to do this is by putting the newly pressed glass back into the furnace entrance, and those parts closest to the heat will turn white.
Slag Glass
Slag glass is characterized by an opaque or translucent glass base with marbelized swirls of a different color mixed throughout. Slag glass cats can consist of two to three colors. The variations can be really apparent or sometimes subtle, depending on how much of a certain color was present when the batch of glass was made. Sometimes slag glass can be different shades of the same color. For example, a lighter green mixed with a darker green.
Slag glass cats were made from the mid-70s to the early 90s. Mosser Glass stopped making them after this point because slag glass cats could be incredibly challenging to create. They would often have compatibility issues when mixing colors; this would cause frequent breakages and losses in the cats during production. It could be very costly because of this. Due to the fact they are no longer being produced, as well as their gorgeous colors and patterns, slag glass Mosser cats tend to sell the very highest and are very sought after.
Opalescent vs. Slag Glass Comparison
When comparing opalescent vs. slag glass, remember that the opalescent effect is on the surface of the glass only, never underneath it. It's almost like a translucent white highlighter. Slag glass will have the white slag (or a different color) swirled throughout, often underneath the glass. Look closely at the images above for comparison. The last image shows a close-up of the feet. You can see that the opalescent example has a translucent white that sits on the surface of the feet. The slag example has white slag that sits under the surface of the glass. It's also mixed with the base color.
Opaline Glass
Few Mosser cat colors can compare to the sheer beauty of Golden Opaline. Opaline glass gets its distinctive iridescent milkiness from opacifying substances added during the mixing process, including sodium phosphate, sodium chloride, calcium phosphate, calcium chloride, tin oxide, and talc. The glass can take on different colors and present variable shades, depending on the mixture and quantity of the opacifying material substance. This Mosser cat looks like it has opalescence in the glass, but the process of creating this effect is very different from opalescent glass. You will notice that the cream areas do not sit on the surface of the glass like they do in opalescent glass but inside it. The feet are also clear, unlike opalescent glass. When held up to the light, Opaline glass shows its translucency and has a pinkish-red or orangish tint (pictured right). This is where Opaline glass gets its nickname, which is “fire glass.”
Milk Glass
Milk glass is believed to have been made at least as early as the 1500s in Venice, Italy. It was originally introduced as a lower-cost alternative to porcelain, which was highly prized and being imported to Europe from China. Milk glass often appears completely opaque. However, it can also show various degrees of translucency, permitting some light to shine through when held up to a strong light source. Milk glass comes in a variety of shades besides just white. It can also be blue, green, light orange, pink, purple, turquoise, yellow, brown, and even black. To create milk glass, early manufacturers added arsenic to their standard glass recipes, which yielded a faintly grayish but nicely opalescent effect. Later versions of Milk glass were formed from compounds of bone ash, antimony, and tin dioxide. These composite formulas often resulted in a deeper, more purely white hue.
Mosser cats have quite a few milk glass colors. Pictured above, from left to right, are the following: Milk Glass, Blue Milk, Jadeite (yes, it's milk glass too!), and Crown Lilac, which was an oops color that was supposed to be Crown Tuscan Pink. Crown Tuscan Pink is also a form of Milk glass.
Alexandrite Glass
Translucent Alexandrite glass appears lilac (or sometimes pink) in natural sunlight or yellow artificial light. It looks smokey blue in fluorescent or white light. This is due to the presence of Neodymium oxide (Nd²O³) in the glass. Some cats are naturally more purplish, while others look more pink. The more purple cats have a stronger reaction to the fluorescent lighting and turn a brighter blue. Please see the images above for color comparison in different lighting. This was a custom-made color for The Collector’s Addition in 2003. At the time, the cats were sold to help fund a surgery that the owner's cat "Sylvester" had to undergo. Each cat came with a special card, pictured below. Some cats were also signed with "2003," "TCA," and a number using a silver Sharpie. If you would like to learn about the causes of color differences in glass, please check out our Unique Factory Traits page to learn more.
Image of a Collector's Addition card graciously provided by Kim Dyer.
