Butane vs Screw thread Canisters: Key Differences
Aerosol-type (MSF-1a / A4) butane canister
Aerosol-type (aka “MSF-1a” or “A4“) 227g butane canisters (pictured left) contain 100% liquefied butane gas. They are available in many different brands. But because they are manufactured to a standard design, any brand will fit any brand of table-top stove.
They are different to standard screw thread iso-butane canisters (pictured right) which are commonly used for camping and backpacking.
The most important difference is that screw thread canisters contain a mixure of iso-butane and propane gas. Propane has a boiling point of -42° C (-44° F). This allows stoves to operate at much lower termperatures than stoves run on pure butane. The lower boiling point means that screw thread canisters contain much higher pressure than canisters containing only butane.
Iso-butane/propane canister with 7/16″ UNEF screw thread
Butane: Key Data
- Butane has a boiling point of -1° C (30.2° F) at sea level.
- Gross Calorific Value 49.1 MJ/kg
- Butane canisters contain 227g (8oz) of liquefied butane
- An empty butane canisters weighs 103g (3.6oz)
- Best use: with a remote canister stove for 3-season outdoor cooking & backpacking
Propane / Iso-butane: Key Data
- Propane has a boiling point of -42° C (-44° F) at sea level.
- Gross Calorific Value: 50.4 MJ/kg
- Screw thread canisters usually contain 100g (3.5oz), 230g (8oz) or 450g (16oz) of isobutane/propane mix
- An empty 230g screw thread canisters weighs 150g (5.3oz)
- Best use: with canister-top stoves year round, and below freezing usage
Butane Canisters in Detail
Butane canister: bayonet-type connector
Iso-butane/propane canister with 7/16″ UNEF screw thread connector
Butane canisters have a flat metal ring around the connector, with gap or notch in it. The notch indicates the orientation of an “L” shaped outlet pipe inside the canister. When the canister is on its side, the notch must be facing upwards to avoid liquefied gas from flowing towards the stove (see graphic below).
Using Butane Canisters with Screw Thread Stoves
Aerosol-type butane canisters are the most widely used portable gas canisters worldwide. They are used by the million for table-top gas cookers at home, in restaurants and for outdoor cooking.
This type of table top stove is especially popular with East Asia, but low cost butane gas canisters can be found in camping shops, hardwear / DIY stores, filling stations, and in East Asian supermarkets almost anywhere. They can also be purchased on-line in many countries at very low prices.
The aerosol-type butane canister uses a “bayonet-type” connector. This allows rapid and safe connection and disconnection between canister and stove. This simple connector also prevents wear on the stove’s screw thread from repeated screwing and unscrewing.
(Notice the notch in the flat metal ring around the connector)
To enable aerosol-type butane canisters to be used with screw thread stoves, lanterns and gas torches, KOVEA created the KOVEA Butane Adapter (KA-N9504).
The KOVEA butane adapter uses its patented “Push And Turn” mechanism to make a secure leak-proof connection. The butane adapter also incorporates a safety valve to ensure that when no stove is connected, gas will not escape. Cheaper butane adapters do not have this important safety feature.
(The tab on the side of the adapter aligns with the notch in the canister)
Why are butane canisters much cheaper than standard screw thread iso-butane canisters?
Small size (100g/3.5oz) standard screw thread iso-butane/propane canisters can cost between £3 to £4 each. That means that the fuel inside is more expensive, gram for gram, than a fine Kentucky bourbon or a blended Scotch.
And it is SIX-times more expensive, gram for gram, than the fuel inside a low cost aerosol-type butane canister, for almost the same cooking/heating power.
So why are butane canisters so cheap? There are several reasons:
1. The butane canisters themselves are cheaper to manufacture because they contain less pressure (2 atmospheres) than a screw thread canister. The propane inside a screw thread canister has a much lower boiling point, so the canister must be strong enough to contain the 4 atmospheres of pressure which results. The bayonet-type connector is also simpler and cheaper to manufacture than a screw thread connector.
2. Butane canisters are used in a domestic setting daily, especially in East Asia. They are manufactured in volumes of hundreds of millions of units annually. They therefore benefit from great economies of scale. Screw thread canisters are a relatively niche product for occasional use (e.g. camping or mountaineering). They are manufactured in much lower volumes, and are therefore more expensive.
3. Butane canisters have become a commodity-type product; so customers usually buy the cheapest they can find and they buy them in bulk. Screw thread canisters are an occasional purchase and are heavily branded by stove manufactures; consumers are encouraged to pay premium prices for these branded canisters.
4. Butane canisters are sold through a wide range of retail outlets including convenience stores, supermarkets, grocers, hardware stores, street markets etc. As they are readily available and competition is high; retailers make very little money on each unit they sell. By contrast, screw thread canisters are sold in small volumes in outdoor gear shops. As volumes are much smaller and unit costs higher, outdoor retailers need to make more money on each canister they sell.
This is why screw thread canisters are 3-4 times the price of humble butane canisters for the same amount of cooking power in above freezing conditions.
Butane canisters can be used at lower temperatures at higher altitudes.
Physics is on the side of low cost butane canisters. Butane itself has a boiling point of just above freezing at sea level. This means that in above freezing conditions, there will be sufficient vapour pressure in the canister to allow butane gas to flow to your stove.
If you try to use butane canisters at temperatures well below freezing at sea-level, nothing will happen. There is insufficient ambient heat to boil the liquefied butane, vapour pressure in the canister will be zero, and no gas will be produced. The stove won’t work.
Atmospheric air pressure declines with altitude. The lower pressure allows the liquefied butane to boil at progressively lower temperatures. The rate at which boiling point reduces with altitude is described by the Trouton-Hildebrand-Everett (see graphic below). This shows that with a humble butane canister you can use your stove at, for example, -8° C (16.7° F) at 9000ft / 3000m on the John Muir Trail.
By pre-warming the butane canister in a sleeping bag or jacket, it can be used at even lower temperatures at such altitudes.