Word soon got out and farmers began to sort through their paddocks and sheds. In the 1970s hundreds of thousands of old bottles flooded the market, sold mainly through a Parramatta auction house. Another prime source was Broken Hill, where unemployed miners scoured the mountainous municipal tip.

The scene today for collectors of antique bottles is very different.

There are bottles considered so rare that single items have fetched more than $25,000 at auction. Even comparatively common bottles can command high prices because all serious collectors want one. An example is the so-called Dempsey Dog bottle produced in Kalgoorlie circa 1910. One sold recently at auction for $18,000 after a bidding war.

The reverse situation also applies. The blue castor oil bottle every collector had to have was valued at $30 in the 1970s. Today these can be picked up at markets for $5.

At the top end of the scale are the very rare or historically significant. Their value has jumped to astronomical heights in the past few years as it becomes obvious that their numbers are finite.

These include some of our earliest bottles, glass or stone, from the convict era. The highest prices are usually for those branded clearly with a known potter's mark or manufacturer's brand.

If the potter's name was Moreton and the ginger beer inside was manufactured by Dunn, that bottle would be worth a small fortune. Moreton and Dunn were convicts and the stoneware bottles produced by this pair about 1840 are exceptionally rare.

In the 1980s, one would have been worth about $900. Today prices go as high as $25,000. For those who bought one 20 years ago, that's a pretty good investment.

Another in this league is Jonathan Leak, a Staffordshire potter who was arrested for burglary and had his death sentence commuted for life transportation to Australia. He arrived in Sydney in 1819 but received his ticket-of-leave a year after because of good conduct.

His Sydney pottery was very successful, turning out ginger beer and blacking bottles, smoking pipes, bricks, pipkins, milk and butter dishes and jars. Any bottle marked Leak (no pun intended) is well worth having.

Most antique bottles are now traded between long-standing collectors, either privately or at public venues such as collectors' fairs or markets. New collectors are usually faced with buying spares from more-established collectors or going through the auctions, where items are often obtained when collections are cashed in as part of an individual's superannuation or estate.

Graham Lancaster Auctions in Toowoomba is the main specialist auction house for antique bottles in Australia (see gdlauctions.com).

Generally a bottle needs to have been produced more than a hundred years ago to be "antique", although any made before 1920 are also valued highly.

Machine-made bottles became established around 1920; before then glass bottles were either free-blown or blown in moulds, which adds greatly to their collectability.

Collector and author David Jones says there is a certain mystique to antique bottles as, unlike coins or stamps, the quantity and type of bottles made is largely unknown. In some cases, all that is known is what is engraved on the bottle. Only from a study of this information can the rarity and desirability be determined.

Its value can also be determined by those who collect for no other reason than that they admire a particular colour: blue, green, amber or white. They are mainly interested in the effect it has when displayed against a kitchen window. The colour of a bottle can increase its value by as much as 20 times.

The appeal of purple bottles is particularly strong. These were originally blown in normal-coloured glass with a small amount of manganese added to make the glass clear. Over time the sun's ultraviolet rays react with the manganese to turn the glass a delicate pink to the deepest purple, depending on the exposure and quantity of manganese used.

Other collectors specialise in one or more of the contents, including quack medicines, inks, beers, wines and spirits, cordials and aerated waters, ginger beers, fruit and preserving jars, food jars, sauces and fancy salad oils. Beer bottles are probably the most popular sub-section.

Condition is another contributor to the worth of an item. Surprisingly, bottles dating from as far back as 1850 have been found in mint condition.

The biggest event of the year for bottle collectors is the antiques fair held on the weekend of August 22-23 at the Penrith Panthers Exhibition Pavilion on Mulgoa Road, Penrith. This event attracts collectors and dealers from all over Australia.

My Collection

David Jones was born in Paddington in Sydney in 1949 but spent his childhood in the bush and cow paddocks of Sydney's western suburbs. It was there that David taught himself oil painting in an old aviary he had converted to a tiny studio.

After three years at Sydney's National Art School, he worked as art director before starting his own advertising agency with two partners in 1979. When he retired in 2002, the business was turning over $27 million annually.

His passion for collecting bottles began in the 1960s when his family went on camping trips around Bathurst. On one trip he explored the ruins of an old goldfields-era homestead, where he discovered his first bottles.

"I was hooked," he says. "I had always had a fascination with archaeology and history and the bottles had me intrigued."

Over the years he began to specialise in collecting soft drink bottles from the Sydney region and after almost 30 years of research he has written a complete history of this subject. A massive 1040 pages that contain about 3500 images, Thirsty Work was published in May.

It is available through thirstywork.com.au for $265.

$30

The so-called "stick bottle" was a patented design by Barrett & Co designed to keep aerated water fresh. This is a fairly common type. Rare specimens in blue- or amber-coloured glass are worth about $6000.

$150

Sydney brewer Tooth & Co Ltd also sold cordial and aerated water in a glass marble-stopper bottle patented by Hiram Codd in 1872. This one has added value because of its original paper label.

$8000

An absolute rarity is this cork-sealed soda or aerated water bottle produced by David Evans in Redfern, circa 1880. Only a handful are known to exist.