Which burner/gas to use for gas forge

[Solingen1871]

Hi guys,

I'm new to knifemaking and just starting out. I have already finished the first blanks which are, at least theoretically, ready for heat treating. I could send them off to a professional knife maker to let him do the heat treating but that would cost me 20 ? - 30 ? per blade. So I figured I might as well get some inspiration from YouTube and decided to build a primitive "gas forge" using gas concrete bricks I had lying around. I used the same method as shown in this video: https://www.youtube.com/watch?v=1qZVcQdvuyc

I also bought a burner with some mulitgas (30 % propane, 70 % butane) from the local hardware store (see pic enclosed). The thing is: I can't get the #### thing up to temperature. Even after 20 minutes of pre-heating the forge and placing thin piece of steel inside for 15 minutes I can't get it hotter than a very very dull red, which is barely noticeable.

So my question is: Is it the burner, the gas I use, or both?

Thanks in advance!