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Glass Process
A BRIEF DESCRIPTION OF THE GLASSMAKING PROCESS

NOTE: This information has been found in a file of old Club Newsletter – this one from the Northern California Club, dated 1989.

The chart was compiled by one Art Edwards of Fenton Art Glass Co. …..It is certainly worthy of reprint here. Enjoy!

A BRIEF DESCRIPTION OF THE GLASSMAKING PROCESS
ACTIVITY
AT WHAT TEMPERATURE
REQUIRES HOW MUCH TIME?
Ingredients weighed and mixed
at room temperature
approx. 30 minutes
Loaded into melting furnace
approx.  2000 deg. F.
approx. 5 minutes
Melting and refining takes place
approx.  2500 deg. F.
10-35 hours,
depending on type of glass and type of furnace
A group of men make glassware.  They draw the glass from the furnace in
gobs ranging in size from 3 oz. to 90 oz. In some factories the glass flows from the furnace into forming machines on a
lower level.
approx.  2000 deg. F.
Men work 8 hour shifts
Each gob is formed into a basic shape by a man using air or mechanical force. In factories making less complicated shapes
or higher quantities, this forming is performed by machines.
approx.  2000 deg. F.
5 to 50 seconds
The basic shape is reheated and changed to the final shape.
1800 deg. F.
20 to 60 seconds
The piece is put in an annealing lehr to strengthen the glass and to cool it off.
1000 deg. F. to room temperature
1 hour to 6 hours or longer
The piece is then inspected, packaged and shipped.
room temperature
1 day to weeks
The main ingredients used and their approximate percentage of the total batch are:

Sand (SiO-2) 75%
Soda Ash (Na-2-CO-3) 15%
Lime (CaCO-3) 9%

Some manufacturers substitute potash for soda ash, and barium or borax for lime. In some opaque glasses, fluorspar and feldspar are substituted for lime.


The color controlling ingredients are mixed in with the main ingredients before melting. Some of the material used to create certain colors are:

MATERIALS
COLOR PRODUCED
Uranium
 Yellow
Cobalt
Blue
Sugar and Iron
Amber
Neodymium
Pink
Iron
Green
Gold
Red
Selenium and Cadmium
Orange
Selenium and Manganese
Crystal
Alumina and Fluorine
White
COLOR
COLORANT
Burmese
Pure gold and Uranium Oxide
Custard
Uranium Oxide
Amethyst
Manganese Dioxide
Ruby Overlay
Gold and Crystal Glass
Blue Satin
Copper Oxide
Cranberry Opalescent
Gold and Calcium Phosphates
Colonial Blue
Copper
Colonial Amber
Sugar

 
UPDATE - August 16, 2015

Boyd Glass in Cambridge Ohio

Hello,

My name is Bob Applegate and I worked at Boyd Glass in Cambridge Ohio for about the first 8 or 9 years they were open. Anyway, I just wanted to let you know that I found your website and thought the information on it was very useful. I think it is great that someone cares enough to compile the information and then share it with others. With the Boyd’s ceasing glass production this year, I am afraid that glassmaking by hand is becoming a dying art in the USA. And with younger generations being collectors of electronics in place of glass, I am really afraid that trend will continue. I hope not. I hope this is just a downward trend comparable to the Depression, WWII, and other times, but I am afraid that may be an unrealistic hope.

That being said, the information on the chemicals needed to produce glass as compiled by Mr. Fenton is a very good article. However, I am sure that you are aware that the most common way for glassmakers in the 60’s, 70’s, and beyond to make red glass, whether it is a ruby color or an amberina style red, is to use a mixture of Selenium, Orange Cadmium and a few other rare earths. Sometimes the pieces will need to be “warmed in”, or reheated after being removed from the mould to bring out the rich red color but not always.

As I said, I am sure that you already knew that but thought I would share the information anyway. We made quite a few red colors of glass at Boyd’s and although saying the use of gold to make the red color seems romantic, expensive, and historic, it is not always the case for all red colors. Some reds require gold yes, but very few.

Again I want to thank you for taking the time and trouble to compile all of the information on your website, and for sharing the knowledge you have gained over the years of collecting glass. It is very, very generous of you.

Bob




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