It's a steep learning curve.... but check another "don't" or "do" off the list.
Yes --- you had HEAT and Fumes (think machine oil from the tube process) blowing out molten metal.
Do you ever wonder - how I can figure these things out BEFORE you post pics of what you were working on??
I buy NON Chlorinated brake clean by the CASE ($1.99 a can if you catch it on sale) to shoot down inside stuff like this BEFORE welding. And either you can drill a small escape hole -- or leave the last tiny bit open - let it all cool down and go back and touch it up.
