Just watched it and

Its just what i needed very informative ,

Will it be possible to buy a dvd when its finnished ?

Nice graphics at the start!!

I loose sound for a minute or so at 4:20.  Again at 15:00 for 10 seconds.  tried reloading it but still the same.

Also you sped up the infusion.  How long was it in real life?  Might be useful to edit the commentry to mention it to reassure people they are doing it right if it seems like its taking a while for them.