This is a Primus 340 SP, plated version. The date code stamped on the base of the tank is AH, indicating manufacture in 1943. These stoves first appeared during the Second World War and remained in production for at least several years thereafter. The stove consists of a Primus 210 tank combined with a Primus 3025 alcohol burner. The burner features a single vaporizer tube, a regulating valve, an internal cleaning needle, and a green, Primus-embossed control spindle. In addition, the centre tube of the inner cap extends to very close proximity to the nipple, thereby serving to restrict the air intake. Please note that on the 3025 burner, the control spindle is positioned to the right of the nipple. In my personal observation, this configuration appears to make fine flame adjustment slightly more difficult. This is a very fine stove; however, it can be somewhat finicky when it comes to maintaining a consistent burn when using modern alcohol fuels. This behaviour is likely due to differences between Swedish fuel alcohol of the 1940s and modern alcohol formulations. The precise reasons for this are not definitively known, as detailed contemporary fuel specifications from the period are scarce. I should note that I am not a fuel chemistry expert; however, several technically plausible factors may be involved. These stoves were originally designed to operate on alcohol fuels available during and shortly after the Second World War, which were likely based on relatively high-purity ethanol with a low water content. In contrast, modern alcohol fuels often contain higher levels of water, various denaturants, or are methanol-based—which, at least in Japan, is generally what is meant by commercially available “alcohol fuel”—all of which can adversely affect vaporization and combustion characteristics. As a result, modern alcohol fuel may not vaporize sufficiently within the vaporizer, leading to unstable operation, reduced flame output, or difficulty in maintaining proper combustion. This effect is further exacerbated by the relatively large orifice of the alcohol nipple, which was likely intended to compensate for the lower volatility of period alcohol fuels by delivering a greater volume of fuel. In practice, adding a small amount of white gasoline—approximately 20% gasoline to 80% alcohol—can improve vaporization and help stabilize combustion. This practice, however, should be regarded as a practical operating solution rather than a factory recommendation and should be undertaken at the user’s own discretion. I have also posted a separate summary of my observations and research concerning modern fuel alcohols on the Pressure Lamp Discussion Forum. Those who are interested may wish to refer to that post for further background information. Best regards, Shinzo
@gkpllantern do you know if you have the correct nipple / jet installed. Different internal diameters are needed for alcohol stoves compared with paraffin or petrol fuelled examples. Regards John
@z1ulike @Spiritburner @Tony Press @Jeopardy @mr optimus @ROBBO55 Thank you all for your kind words. ーー Jeopardy, Yes, fortunately my 340 SP stove is fitted with the correct nipple (part no. 4419) and the matching cleaning needle (part no. 4420), both of which are standard components for the 340 SP. I appreciate you checking, as the difference is indeed important for alcohol stoves. Best regards, Shinzo
Thanks for the reply Shinzo-san. If you have the correct nipple and the seals are all OK I'm not sure what else you can do. I hope that you can get it sorted ready for using it at cherry blossom season. Regards John @gkpllantern
@Jeopardy Thank you, John. Mechanically everything appears to be in good order, so I believe the issue is most likely fuel-related. In practice, I have found that using a high-ethanol alcohol works better, and if the fuel appears to be methanol-rich, adding a small amount of white gasoline can help improve vaporization and stabilize the burn. Of course, this is simply a practical operating adjustment rather than an original factory recommendation. I will continue experimenting carefully. Best regards, Shinzo
@gnome Thank you for your kind comments. I am continuing to research Sweden’s alcohol fuel situation during and shortly after the war. It may take a bit more time, but I hope to share something once I have a clearer picture. Br, Shinzo
