Advice on false bottom for mash tun - correct perforation diameter?

[fungalboy]

Hi folks,
I'm putting together a mash tun and I have acquired a sheet of perforated stainless with 3mm holes. I've seen people selling 2mm versions on line and i dug out an old brewing book that i had which advised 0.7-2.0mm holes so i'm a little on the large side. I'm pretty sure that it will be fine but would like any advice that people might have.

Do people have any experience with varying diameters? Should I bother trying to source a lower size?

Thanks.

[LordEoin]

you'd probably be fine but have a lot of grain matter getting through 3mm holes.
maybe something like this over it might improve it:

[biertourist]

The Malt Miller's custom false bottoms for the thermobox mashtuns had 1.5mm holes.

I spent a lot of time on false bottom design and I ended up with 0.06" (15 gauge / 1.5mm) thick perforated stainless with staggered holes -the hole size in inches was 0.09375" (3/32" or 2.4mm) with an 0.15625" (5/32" or 4 mm) stagger. 

This gives you a 32.6% open area.

In my notes I noted that the hole size was a little bit on the small size but still shouldn't clog.  I LOVE my false bottom but I know if I would've pushed a bit more I could've had an even higher % open area but possibly with a bit more clogging.  You should try your 3mm hole false bottom as is first and see how it works.

-If you don't already: condition your malt! It will help get you fully intact husks which will work better with the larger hole size -just spray 2% water by volume over your whole uncrushed grain and mix it well and let it set for 10-20 minutes before you crush it. You will get beautiful whole intact husks which should help.

If you're going to recirculation mash, you want a large % open area; a larger % open area will also help you run off faster without getting stuck -unless you get there by getting too large of holes in the FB and then grain pieces start to get stuck.



Adam

[fungalboy]

Thanks folks.

I'm going to give it a lash and see how it goes. If needs be I've found some 2mm SS sheeting on RS-online that should do the trick.

Will

[phelixoflaherty]

sheet with 3 mm holes. get two pieces . join them with bolt thru centre hole. turn them in opposite directions. you can now vary the size of the 3 mm holes.
cleaning it might be awkward though

[Will_D]

Great idea about the two sheets. Cleaning should in fact be much easier. Just undow the bolt!

I used the garden hose at the compost heap for the 95% wash!

Then its inside with warm water a cleaner. (Lidl's W5)