Butane blowtorch condensing liquid on heating surface I have a small Butane blowtorch, and use it to heat an Aluminium plate. The plate is thick so takes 20 seconds or so to really start heating up.

As soon as I apply the heat, droplets of some liquid start "condensing" on the surface of the metal around the general area of the flame.

The liquid is colorless and odorless and is at room temperature, note this happens when the metal is still at room temperature as it hasn't heated up much yet.

What is this liquid exactly and why/how does it form? I suspect it could be a $C_{4}H_{10} + O_{2}$ reactant but not sure.  Thanks!
This is a guess - but I think it might be water formed as a byproduct of butane combustion precipitating on the plate:

$$
\ce{2C4H10(g) + 13O2(g) -&gt; 8CO2(g) + 10H2O(g)}
$$

Aluminum has very high thermal conductivity, so it is possible that the plate is rapidly absorbing heat from the water vapor, causing it to condense. If this stops happening right around the point when the aluminum temperature reaches 100 C, that would be evidence to support this hypothesis.