What exactly is "Flint Glass"? John and Elizabeth Welker describe it as such in their book  (Pressed Glass in America, c. 1985, Antique Acres Press): "This is the term for a specific type of glass.  The name was said to have been derived from the fact that in England in the late 17th Century that flint, a form of hard, very pure, natural quartz, was calcined and pulverized to make silica as a main ingredient in glassmaking.  Use of this pure silica makes glass highly refractive and brilliant. This English formula also employed oxide of lead as another ingredient.  Thus, the anynonymous relationship between the terms Flint Glass and Lead Glass, although flint and lead each have a different role in glassmaking.  This name applied to fine quality lead glassware in the 18th Century.  In early advertisements, clear or crystal glass was called flint.  The term flint was also used after 1864 (when successful lime glass was developed) by dealers to incorrectly describe this new lime glass.  Technically, Lead Glass is the most correct term in describing flint glass in America.  The general type of glass containing lead oxide as a principle ingredient apparently never contained the raw flint material here.  Thus, the term
flint is a misnomer. The synonymous use is simply an accepted description by traditional use of both terms.  Here, flint generally refers to a lead-based glass, even though it has been used when referring to lime glass."
Canary glass was the term originally used for flint glass that contained uranium oxide to produce a yellow-colored glass.  When the glass formula using lime for production  began in 1864 (first produced at Hobbs, Brockunier and Co., Wheeling WV), the glass that was yellow had a more pale tint to it and had a bit of a green flash when exposed to sunlight.  As the modern-day use (meaning after 1800) of uranium oxide in glass formulas was not used until shortly after 1840 at Boston & Sandwich, Sandwich, MA, Canary Flint Glass can be generally put into a time frame between
1840-1864.  There was some overlap after 1864 (up to about 1870), but generally glass factories had generally switched over to the lime formula by 1870.  This was due to a couple of factors:  the shortage of lead from the Civil War, and lime glass could be produced at a tremendous savings. About five times as much lime glass could be produced for the price that flint was costing to produce.  This also enabled the middle and lower-class families to afford glass for their homes.
Sometime after 1864 and before 1900, the term VASELINE came into usage as a way to describe this canary-lime glass color that wasnt really the same as canary flint  glass. The older canary flint glass was a much more bold, bright yellow color than this new lime-based canary glass.   This was a topic of major discussion during the times and the term VASELINE was primarily a dealer term that more than a few people objected to.  In the book, OLD GLASS, Copyright 1924, by N. Hudson Moore, page 349, it states:
"All the pieces shown in figure 207 are in this royal purple and canary yellow, which, by the way, no real collector would ever call vaseline, a dealer's term."   This is also the oldest reference I have found that uses the term, VASELINE, to describe this type of glass.
Canary flint glass WILL glow bright green under a UV blacklight and for all intents and purposes, is collected by vaseline glass collectors as a "yellow-green glass that will glow green under a UV blacklight, due to the presence of uranium oxide in the glass formula (definition most widely used by vaseline glass collectors). Due to the content of lead in the glass, the glass has a softer feel to it.  The flint glass made before 1864 had as much as 40% lead oxide in it (as compared to todays lead crystal, which generally contains a maximum of 24% lead). Canary flint glass was
also much thicker than the vaseline glass made after 1864, but this was primarily due to the lack of refinement in the glass presses of the day, rather than a necessity of working with molten glass with a high lead content. The glass produced during this time frame also seemed to have had more simplistic patterns, which I also think was  due to the lack of refinement in the glass pressing procedures of the day.
In the book, Pressed Glass In America (John & Elizabeth Welker), these observations were made regarding the physical analysis in dating glass: If a pressed pattern is made from lead (flint) glass which is noticeably heavy and normally rings when tapped, the chances are good it was made before 1870.  Flint glass pressed ware has been made over the years since, and is still made today, but in very limited quantities.  Conversely, non-lead or lime glass which does not ring when tapped was formulated for factory
production circa 1864, which establishes the earliest date for lime glass in pressed tableware. If the item is flint and non-Lacy (i.e., a pattern such as Ashburton), the period slowly began in the early 1840s and continued until circa 1870. If the item is made of colored lime glass, it can be dated as early as 1870. There were comparatively few items in color during the flint glass period, including Lacy glass. What we can infer from this information from the Welker book is that there was very little colored flint glass made during the period that Canary Flint was produced (1840-1870).
The three companies that seemed to have made most of the Canary Flint Glass that we find today were the New England Glass Co. (East Cambridge, MA), Bakewell,  Pears and Co. (Pittsburgh, PA), and the Boston and Sandwich Glass Co. (Sandwich,  MA).  There  was  also a notation in the Glickman/Fedosky book (Yellow-Green Vaseline: The Glass that Glows, published by Antique Publications) that McKee also made some canary flint
More has been written about the Boston and Sandwich Glass Co. than probably any other glass company in history.  If you would like to learn more about this company, I would suggest you go to your nearest public library and see if they have any of the series of books by Barlow and Kaiser (still in print, but expensive to buy them all).  There is also a good book by Ruth Webb Lee on this company.
Canary Flint is an illusive thing to find, but you can still find it.  It
will either be identified as canary flint and you will pay dearly for it,
or it will not be properly identified and you can find some real bargains. I have seen a Boston and Sandwich master salt sell for $147.50 and two months later, I bought a similar one that was made by Bakewell, Pears, & Co. for $15.00.  The first one was identified as Canary Flint, the second one was not.
Antique shops are generally going to know what they have before they put an item out for sale, so expect to pay full retail (or more) if you come across a piece in a shop.  If you do find a piece in an antique shop or mall, decide then and there if you are going to buy it.  Chances are that it was just recently put on the shelf and that it will not be there for long, no matter what price is listed.
Monthly antique shows are another location to look for good flint glass. Chances are better here than in an antique shop to find a bargain, as it may just be listed as a yellow piece of glass, due to the fact that it does not have the usual yellow-green look of vaseline glass (at least under florescent or incandescent lighting).  I have yet to come across a piece at a weekend show, but that does not mean they will not show up.  Again, decide then and there if you are going to buy it, because the traffic at these shows will mean that it probably will sell very early.  At a local monthly show in OKC, I heard that a dealer (on Friday evening preview early-bird time) found another dealer selling a PAIR of Boston and Sandwich
candlesticks (with the wafer that joined the top and bottom half together) and got them for under $50. These usually sell for a minimum of $200 each. A side note: I mentioned the wafer in the previous paragraph.  A lot of this early canary flint glass that was made by Boston and Sandwich and New England Glass were made as two separate pieces. They were then joined together with a glob of molten glass and pressed together.  When pressed,
this would form a thin wafer of glass that would hold the two pieces
together.  This will be a smooth area between the top and bottom portions that will look somewhat as part of the total item, yet will have no pattern molded into it like the top and bottom portions.
The best place I have found for Canary Flint is on-line auctions. However, if you do a search for typical names like SANDWICH, CANARY, OR FLINT, be aware that others are also searching these key words. The best deals will be where they have not properly identified the piece, or put it under the wrong category. Some of the best deals I have gotten was because the item was under the wrong category, it was not identified properly by the seller,
AND it was a little out of focus or the picture was dark.  I knew what I was looking at from doing the research.  If the glass looks very thick, is a bright yellow that does not show any green (taking the photo indoors under incandescent light will totally eliminate any of the green UV flash) and has a somewhat simplistic design without a lot of detail. This is your clue to start looking further.  You do not have to know what it is right then, if you spot it shortly after the auction starts.  After all, that auction will probably run 7-10 days, which gives you some time to do the research.  You can save a photo or print it out and can then take this information to the library or an antique dealer you trust and see if he/she can help you identify it.  Once you get a possible name of the pattern or
manufacturer, you can research further in reference books or ask fellow glass collectors on the internet (without divulging where the piece is located for sale!).  This PRESSED BALL AND GROOVE master salt on pedestal was purchased on ebay by me for less than $50.  It has a value of $375, according to Barlow and Kaiser in their series of books on Boston & Sandwich Glass.  In an email disussion with a long-time flint glass collector, this person told me that he had a damaged one in canary (one petal broken off) and the only one he had seen besides his was at the B & S Museum in Sandwich MA.  This master salt is on the far left of the picture
shown in this article.
To close, I would like to say that anyone who collects vaseline glass or flint glass should try to add one piece of Canary Flint to their collection as an example of a true antique from a time gone by that will never be here again.
Researched and written by Dave Peterson, Vice President, Vaseline Glass Collectors Inc.
A  Guide  to  Sandwich  Glass  (Witch  Balls,  Containers  &  Toys;
Colognes and Stoppers) by Barlow & Kaiser 1987, Barlow & Kaiser Publishing Co., Sandwich, MA)
Sandwich Glass, Revised Edition, by Ruth Webb Lee, c. 1939 by Lee Publications
The Romance of Old Sandwich Glass, by Frank Chipman, c. 1932 by Sandwich Publishing Co., Inc.
For more information about Vaseline Glass or the Vaseline Glass Collectors, Inc.:
you can email the author at <>
Photo identification: Back row, left to right:
BOHEMIAN DECORATED TUMBLER, museum quality (c. 1845)
PILLARED LOOP SPILL green canary, possibly Boston & Sandwich (c. 1850s)
Middle row:
TOY SPILL or WHISKEY TASTER, possibly Boston and Sandwich (c. 1850s)
BLOWN MOLD COLOGNE, Boston and Sandwich, (c. 1840-1870)
MASTER SALT, Bakewell, Pears, and Co. (c. 1870)
Front Row:
Pair of TOY TUMBLERS, Boston and Sandwich (c. 1845-1870), notice the opalescent tint on the one on the left.
This article was condensed from an article that appeared in the GLOWING REPORT, March 2000 (the official publication of the Vaseline Glass Collectors, Inc.)
copyright 2000 by Dave Peterson and VGCI, all rights reserved