Quality Control

Over the years insulators have been produced, the quality has increased.  In porcelain, designs have been standardized, production dimensions have fallen into tighter tolerances, air bubbles have virtually been eliminated through the use of wet process porcelain, and glazes are more uniform.  In glass, impurities were decreased, clear became the standard color, and production dimensions also had to conform to tighter ranges.  Below, data on different information is provided for the researcher interested in this issue.

Weights were taken of clean, mint condition insulators using an electronic Pelouze postal scale that digitally displays weights to a tenth of an ounce.  Occassional checks of the scale were made involving weighing a particular sample numerous times to determine the extent of measurement error.  In about 1 in 10 insulators that were checked, an error of a tenth of an ounce was noted, always in the same direction (e.g., always 1 oz more, not 1 oz more sometimes and 1 oz less others).  Placement of the insulator on an off-centered location on the scale was probably responsible for 80% of this since, when care was taken to place the insulator in the center, consistency occurred.  The closeness of the insulator to a midpoint between two possible measures probably produced much of the remaining error.  For example, an insulator that weighed 16.15 ounces could be displayed as 16.1 or 16.2 by the scale.

CD122 [030] HEMINGRAY-16//MADE IN U.S.A.  RDP, Aqua
Weight in ounces Number of Insulators
14.7 0
14.8 7
14.9 2
15.0 2
15.1 5
15.2 9
15.3 13
15.4 2
15.5 0
15.6 0
15.7 0
15.8 1
15.9 0

Sample size: 41 insulators
Average weight:
Mean = 621.3/41 = 15.15 ounces
Mode = 15.3
Median = 15.3

CD 155 [040] HEMINGRAY-45//MADE IN U.S.A./[numbers and dots]  CB, straw
Mold #-Date Code Weight
12-45 1lb, 8.5 oz.
13-45: (2 dots) 1lb, 8.3 oz.
20-45: (2 dots) 1lb, 8.3 oz.
29-45: (2 dots) 1lb, 8.8 oz.
30-45: (2 dots) 1lb, 8.3 oz.
30-45: (2 dots) 1lb, 8.2 oz.
31-45: (2 dots) 1lb, 8.2 oz.