Overnight Mash - unusual film on surface

[beermaker]

Did my second overnight mash last night. Both seem to have gone well, although on the surface of both mashes I noticed a whitish film. I can't for the life of me decide if it was a mould or some kind of protein film or something else. Is this normal? The temperature of the mash this morning was on average about 47ºC and at the surface of the mash was around 38ºC. When sparging the film floated up on top of the sparge liquor, carrying some of the malt husks with it. The conversion seemed good and the wort looks and tastes ok. Just wondering if anyone else has experienced this before, or has any idea what it is and whether I should be concerned. I hope it's ok as overnight mashing is quite family friendly.

 

[Jeltz]

Well I don't know what the film was but I don't get it.

However, I would be adding to the insulation I've read it suggested that to keep the stuff sterile it should remain well over 50°C, while any nasties would have been killed off in the boil if anything did get in there and start feasting its possible odd flavours they produced before the boil could make it through to the final beer.

Fortunately my overnight mashes never fall below 60°C but then again I do BIAB so there is a lot more water to hold the temperature and my insulation is a bit OTT.

 

[beermaker]

Cheers Jeltz : I suspect it was a mould of some description which is annoying! The surface temperature would have been ideal for mould growth, although the core of the mash was still hot enough to retard growth. I think temperature will be the key here - maybe need to look at the insulation on the tun to prevent thermal losses. Also need to get my butt out of bed earlier as at present I'm not getting into the brewery until midday which means the mash is sitting for nearly 15 hours! Heating the tun will be nigh on impossible so perhaps massively increase the insulation on the tun both on top and underneath, maybe mash in just before going to bed and then get in the brewery sharpish the next morning. Will try it and see how things go!

 

[Jeltz]

If you can get some Kingspan or similar wall insulation the thats a great thing to sit the tun on builders skips will often have off cuts

My vessel is a bucket and I have some underneath and a circle cut for the top then I wrap it all up in a hot water cylinder jacket. losses are about 0.5°C an hour but as I said before that's with more water due to being BIAB. This thread shows how its wrapped up overnight.

 

[beermaker]

How fortuitous - I have a sheet of Kingspan which has sat outside the back of my shed for the past 6 years getting on my wick - I was planning to chop it up and take it to the tip this weekend but on second thoughts.....!!! My mash tun is rectangular so will cut some for the base, some for the top and if there's enough left I'll do the four sides too, although it'll be tight as the mash tun just about fits in the existing brewery as it is. Methinks a little measuring up is in order. Will also see about either getting a cylinder jacket or reappropriating an old sleeping bag now the cooler weather is well on it's way. Also thought about pre-heating the mash tun, although not sure if there would be much benefit in this.

Cheers for the link to your brew day, made excellent reading! : my assistant brewers aren't too keen on bonios but they'll do anything for those marrowbone chews!

 

[Pakman]

How fortuitous - I have a sheet of Kingspan which has sat outside the back of my shed for the past 6 years

If the edges were not sealed check it has not absorbed loads of water over that time - it's useless as insulation when full of water.

Graham

 

[beermaker]

Never considered that Graham, cheers for the tip off. Will investigate how dry it is with a damp meter before wasting a load of time. Hopefully we'll be getting some building work done at the farm where I work soon so I can see about bartering some kingspan for ale.... :thumb:

 

[beermaker]

... or failing that I'll cut the bits I need from my board and take them to my folks to dry out behind their rayburn :)