Appropriate size thermometer in mash tun

[freekq]

I'm looking at getting a good quality thermometer to replace my glass thermometer that I haver been using up to now for AG brewing.

I've have a 26 litre esky that i plan on using as a mash tun/lauter although the dimensions are 40wx20dx30h (cm) which I believe is closer to 24 litres.

Can anyone recommend an appropriate thermometer
I have seen in http://www.craftbrewer.com.au/shop/details.asp?PID=885 a thermometer with an 80 mm length. Is this long enough?

Any help is appreciated

[freekq]

Sorry , I forgot to put in the fact that I was planning on drilling a hole into the top of the esky lid and having the thermometer sit on the esky lid with the probe inside the esky

[Kevnlis]

I would suggest a digital thermometer. Doc just picked up a good one from Dick Smith I think? As long as ithas a fairly good accuracy and reads to 0.1C you should be fine.

[rwh]

http://www.extech.com.au/control/products/4039p.php

[drsmurto]

Yep, thats the one I WANT to buy but havent got around to yet. I still use the mercury thermometer that followed me home from work......

I really dont like the idea of those bi metal thermometers. If, like me, you approach brewing from a science background you will understand the term homogeneous. A mash, unless constantly stirred, will never be homogeneous. If you move the thermometer a few cms either way the temp will be different. The mash temp we take isnt as accurate as people make it out to be. Its an average temp. And it depends entirely on where in the mash you place it.

Without going into a nice physics tutorial i would recommend the digi thermometer which you can use to measure mash temp, sparge temp etc.

Nerd hat taken off. I think i need a coffee......

Cheers
DrSmurto

[freekq]

Cheers guys. I'll have a closer look at the link as there are 2 options available.

[Tipsy]

I use the Bi metal thermometer in my tun and check it against my digital one when stirring the mash (it's spot on)
I don't know about going through the lid though. I put mine in the side to make sure the probe is somewhere in the middle of the mash.

[Tipsy]

Cheers guys. I'll have a closer look at the link as there are 2 options available.

The weldless one is the go for a plastic esky

[freekq]

Tipsy,
you have no problems with leaking having the thermometer on the side? It seems like it would seal reasonably well.

Do you have problems with stirring?

[Tipsy]

Tipsy,
you have no problems with leaking having the thermometer on the side? It seems like it would seal reasonably well.

Do you have problems with stirring?

The weldless one has o'rings and lock nuts made for this purpose (so no leaks)
I do bash around the probe when stirring but its no hassle and the probe is so sturdy I doubt I could damage it.

[freekq]

fair enough then. i'll weigh up what type to get. I know in due course (or is that season ) i'll go down the digital path suggested by Kevnlis and Drsmurto, but in the interim the Bi metal thermometer is a good option considering the funds are stretched trying to set up for AG.

Edit: sorry rwh, forgot to give you a mention

[Stubbie]

Hey Doc,

I'm glad I came across your post. A few nights back I brewed a partial version of Boonies LCPA and used a 26L esky as a mash tun for the first time. Until then I did my partials a la stove top in a pot - improvisation by necessity. Anyway, using a standard glass thermometer, I was stunned at the temperature gradient from the bottom of the tun to the top. There was a temperature change of 5C or so, with a low temp at the bottom and hi temp at the top. The observation caused a bit of a panic on my part. Without much experience to fall back on, I was unsure where exactly to place the thermometer and subsequently add either boiling or cold water to adjust the mash temperature.

At first I wondered whether I was getting too much heat loss from the mash tun, but ruled that out pretty much. And I was reasonably confident in my procedures. So I've put my mind at rest, reminding myself that the laws of physics at play in my mash tun are the same as in everyone else's mash tun.

Now, as an engineer, I'm all for accuracy. But accuracy in temperature measurement becomes far less meaningful unless we're consistent in terms of where in the mash tun we take a measurement, I would think. My inclination would be to take a reading from the middle of the mash (that's what I did the other night) as an indicator of average mash temperature. But I'm all ears.

As long as I'm not hijacking this post, would love to hear what others do? I just think the point of temperature measurement is at least as important as having a you-beaut thermometer.

Cheers

[drsmurto]

Noticed the big differences in temp in the mash too form top to bottom. I now stir the mash for nearly 5 mins which ensures thorough mixing (all things being relative). At this point the temp differences are reduced to about 1degC and i reckon thats about as accurate as you need. If i have to adjust the tmep by adding hot or cold water then i make sure i stir thoroughly again.

Cheers
DrSmurto

[rwh]

As long as I'm not hijacking this post, would love to hear what others do?

Stir the mash every 15 minutes. Take readings from the middle. Also, I preheat my mash tun with some hot water swished around before I use it.

[Cortez The Killer]

Mashmaster have released mark II of their weldless thermometer

Looks good!

Cheers

[Tipsy]

As long as I'm not hijacking this post, would love to hear what others do?

Stir the mash every 15 minutes. Take readings from the middle. Also, I preheat my mash tun with some hot water swished around before I use it.

as do I

[Stubbie]

Thanks for the input.

I'm happier now. Was hoping to avoid having to stir the mash, but I suppose it's a necessary evil. Just have to be careful not to create any aeration.

In fact, I just brewed another batch. A good stir made a big difference to the temperature consistency. Am happy to report that I could get the temperature range to about 1 degree C.

Cheers

[drsmurto]

FWIW - the higher the temperature of a liquid, the less gas dissolved in it. And since the solubility of oxygen in water (yes, it will be different for a sugar based solution) is so low (less than 1 mol %) i am happy to not worry about this.

[Trough Lolly]

As long as I'm not hijacking this post, would love to hear what others do?

Stir the mash every 15 minutes. Take readings from the middle. Also, I preheat my mash tun with some hot water swished around before I use it.

as do I

Ditto with my 10 Gal rubbermaid cooler!