Graduations on the inside of plastic vessels

[Tunabeast]

So on my DIY kettle element plastic bucket boiler I have marked external volume graduations, but despite this I find it incredibly difficult to monitor the level during a boil.

It would be nice to try and mark the inside somehow - permanent marker is the obvious choice but I'm pretty sure it'd impart nasties into the brew over time. Might be impossible but worth an ask - anyone got any ideas?

 

[Sadfield]

Dipstick

 

[bikesandbeer]

Dipstick

Bit harsh!!

 

[Bigcol49]

Hi!
Ullage stick - Dutto's solution.
You measure the dead volume at the top of the boiler ad threfore don't need to "dip your stick".
Add 1 litre of water to your boiler, hold the stick at the surface of the water and mark the stick at the lip of the boiler - 1 litre.
Add another litre of water and mark off 2 litres.
Do the same for every litre of water added until you have reached the max limit of the boiler.

 

[Tunabeast]

Cheers - that's a great shout.

 

[Sadfield]

Another option. As your heat source is in you kettle, you could stand the whole lot on a set of parcel scales, and weigh the wort.

 

[foxbat]

I just measure the dead space down from the top with a stainless ruler and note the number of millimetres down on paper. My boiler is a cylinder so it's simple maths in a spreadsheet to know the precise volume.