Chimneys for Flat Burners

The chimneys for the simple flat burners are the so-called bulge chimneys, also called Viennese or Vienna chimneys, because the early flat burners, which dominated the market in the early phase of kerosene/paraffin lighting, were mostly made in Vienna.

This chimney has a cylindrical fitter 1.5-3 cm high at the very bottom. Above the fitter, the Vienna chimney spreads considerably. This wide part of the chimney, called the bulge, is mostly at the height of the flame. The wide bulge serves to give the flame of the burner enough space to develop optimally. A very important factor for the bulge design was also that the glass walls of the chimney should keep a reasonable distance from the hot flame so as not to overheat. Heavily overheated glasses, in fact, tended to crack much more before chimneys made of heat-resistant borosilicate glass came onto the market. Due to this rather wide bulge, there is no compression of the air towards the flame; the flame does not get intensive air contact. The bulge chimney only creates the necessary chimney effect. The bulge of the Vienna chimney becomes very gradually narrower towards the top, so that the chimney only has a smaller opening at the top (smaller in diameter than the fitter at the bottom).

Chimneys for flat burners (shown in their correct size ratio to each other - Top row: marks of the chimneys shown)
From left: Small chimney for 2’’’ Spar burners
Vienna chimney for 11’’’ flat burners of R. Ditmar
Vienna chimney for 11’’’ flat burners in baluster shape
American chimney for #2 central air draft lamps
Duplex chimney with oval bulge for British duplex burners
Victoria chimney of Young, Birmingham, with lipped fitter

A flat burner with its chimney
From left: 11‘‘‘ Vienna flat burner of R. Ditmar with glass chimney
Schematic representation of the air flows and the flame
The flame of the burner from the wide side
The flame of the burner from the narrow side

It goes without saying that different sized burners also need different sized chimneys. The trade offers newly manufactured Vienna chimneys for almost all common flat burners. Very many lamps with Kosmos burners are offered on eBay with a randomly fitting Vienna chimney instead of a proper Kosmos chimney. Due to this circumstance, I have received many Vienna chimneys over the years, which I cannot continue to use after all. If you study the dimensions of these glasses, you are amazed at the variety that exists here! It is therefore only possible to a limited extent to classify these glasses in terms of their relevant sizes.

Chimneys for American Flat Burners

The American flat burners also use bulge chimneys, which hardly differ from the Viennese chimneys in their outer appearance. They are adapted in size to the respective burner size. Old, marked bulge chimneys from the USA are hardly available on the market (at least on eBay portals). However, the American online trade offers a large variety of newly manufactured chimneys in different fitter sizes, bulge widths and heights, so that you can buy a glass chimney of your choice for every American lamp.

Chimneys for Duplex Burners

As explained earlier, duplex burners are flat burners that have two wicks running parallel to each other. The correct chimney for this has been derived from the Viennese chimney; it has the same appearance and shape of the bulge, with the difference that the bulge is not round as in the normal Viennese chimneys, but is pressed flat on two opposite sides, so that it is correctly oval instead of round in horizontal cross-section. The fitter and the upper opening, on the other hand, are completely round. This type of Viennese chimney with an oval bulge was invented by Hinks & Son in Birmingham.

The reason for this very unusual shape of the duplex chimneys is that one wanted to design the distance between the glass walls and the flame in an optimal ratio in order to optimise the air supply to the flame. However, two flat burners standing parallel to each other do not have a round cross-section as in round burners, but rather the shape of an elongated rectangle. The oval shape of the chimney ensures that the walls of the bulge of a duplex chimney have always approximately the same distance from the flame.

Since the duplex burner was most widely marketed in the UK, it is also understandable that the typical duplex chimneys with the oval bulge are most likely to be found there. eBay UK is a very good source for these old chimneys. The newly manufactured chimneys for duplex burners that are available online, on the other hand, do not have the oval bulge. They have a circular round bulge and are more like Viennese chimneys; they still do the job well.

Chimneys for duplex burners
From left: Chimney with oval bulge (wide side) – Chimney with oval bulge (narrow side) – Oval bulge cross-section – Round bulge chimney

A duplex burner with its oval-bulge chimney
From left: Duplex burner of Hinks & Son with oval-bulge chimney
Schematic representation of the air flows and the flame from the narrow side
Flame of the burner from the wide side
Flame of the burner from the narrow side

It is obvious that this oval shape of the chimney should be expected even more for the simple flat burners, because there you only have a flat wick, and the elongated shape of the flame is even more pronounced. And indeed, the first oval-bulged chimney was designed and patented by Hinks & Son in 1861 for the simple simplex burner with one wick. There was no equivalent to this in continental Europe. With the advent of the round burner, optimisation steps for flat burners had become rather obsolete. However, one must also bear in mind that in the early days of kerosene/paraffin lighting, i.e. in the decades of the "Viennese flat burners", such optimisation steps were still a long way off. The flame of the flat burner spread a rather weak light, only slightly superior to the candle flame, because the inner air flow of the round burner was not available to this flame. The fundamental optimisations with much larger wicks in round burners, flame widening discs, glass chimneys optimising the chimney effect came much later.

Chimney Sizes

In the following tables I have compiled the relevant dimensions of the chimneys for flat burners. I have used the chimneys that I have in my collection as a basis. For the American chimneys, I have used the information in the known literature in cases where I do not have a chimney at all.

Table A: Glass chimneys for European flat burners

* There are also duplex Bijou chimneys as bottle-shaped chimneys without bulge.
** This is the largest of 4 Victoria chimneys of Young.

Table B: Glass chimneys for American flat and center-draft burners

* #2 and #3 flat burners have the same chimney size. The burners differ from each other only in their thread size for the font collar.
** Taken from literature.