steam4....to save reinventing the wheel....try this WEB site
http://miniaturesteammodels.com/index.htm1. Select Boiler Fittings & Materials
2. Select Refillable Gas Tanks
3. eg., select 4260 Tank
4. Select Gas Tank Refillable Instructions
Not that I am biased...being an Australian WEB site, however it is pretty straight forward
If you visit some French WEB groups you may see other procedures using larger gas containers inverted & transferring gas [but in a liquid state
as opposed to boiled off Propane/Butane......
We in OZ, extract & liquefy our LNG....they transport it to Korea, it is decanted to 220gm disposable containers & exported back to OZ & sold for approx. $1.20 AUD each [in a pack for 4]......if you go to a camping store the have 250gm containers for $8.00 AUD
My refillable gas tank has a published capacity of 105gm...I have been able to achieve a 103gm transfer [by weight on digital scales] & so the disposable tank still has ~~ 1/2 it's weight in gas available for the next refillable recharge....[the second filling is more problematic
in terms of optimum temperature of both the disposable and the refillable tanks]
So for my money...pretty good value
Derek