Any tips on unblocking sink -- desperate, it's nearly teatime

[bakedpotato]

A plumber had agreed to come, but his mobile is now switched off and he's 20 mins late so is obv starting w/e early.
I've tried caustic soda, plunging, run out of ideas

Boiling water, which helps to melt any greasy gunk

the sink is 3/4 full of black water and smells rank from the caustic soda
am scared of blowing house up if i put anything else in, do you think i should be rash and chance it?

no room for the boiling water

syphon some of the water out

How about using a pot or bowl to empty some of the water from the sink first. I know I'd rather get rid of most of the water than risk it overflowing!

Then pour boiling water in to see if that helps?

Don't add any more chemicals to the caustic soda. very important that you don't add bleach

www.diynot.com/pages/pl/pl005.php

Migh give you some ideas

oh Dinosaur so kind, does he travel to N London?
Mind you no plumber is going to come out at this time of day on a friday
Thank you HMB for chemical advice
would like to know why this sort of thing always happens late on fri afternoon

(whoops, plumber may be a she of course )

instead of typing 'wink' i just typed 'sink'