Is 97C enough of a boil?

[AJ80]

G'day all,

In prep for my first AG tomorrow, thought I'd give my OTS element (2400kw) a crack in 30L water in my 50L keggle. While what I achieved was a slow boil, the temp would not go above 97C. I've already insulated the keggle with a camping mat to help. The water in the pot was definitely moving around (I.e. There was a convection current of sorts).

Previously, I've done all extract brewing with a 10L boil on the stove without any issues hitting a strong rolling boil.

My question is whether 97C and a 'not quite rolling' boil (SWMBO has told me I can't even call it this as it didn't hit 100C) enough or should I seek another element? Have read about an aluminum pie dish floating on top can help, but I don't have one.

If I get time this evening I'll post up a couple of pics of the three tier brew stand I knocked up yesterday with the bro in-law.

Thanks in advance guys.

Cheers,

AJ

 

[manticle]

You need it to move and you need to get a certain amount of evaporation. I've never needed to do it but Thirsty Boy posted a little while back about achieving a rolling boil on a weaker stove by floating an aluminium takeaway container on the top of the wort.

 

[warra48]

A boil is a boil when it is boiling.

It is not temperature dependent on its own, and a boil can happen at different temperatures, depending on the atmospheric pressure etc., not necessarily at 100ºC specifically.

Thus, if it looks like a boil and you have bubbles breaking the surface, and you are losing volume to evaporation, then you have a boil.

 

[Nick JD]

If you get a big (like 50ml) syringe and put 20ml of water in it and then pull the plunger back hard it'll boil.

AJ - what you need to do is a full-length boil of 60 or even 90 minutes and measure your evaporation rate.

Also, are you above 500m in altitude?

 

[treefiddy]

If you're sure the thermometer is correct, do you live somewhere elevated (Great dividing range, Mt. Doom etc.)?

You can make a little foil boat out of aluminium foil, just fold in the sides. It worked pretty well when I stated out.

 

[Florian]

Doesn't need to be aluminium either, you can use plastic takeaway containers or any other tupper style lunch box or whatever.

BYO health concerns.

 

[AJ80]

Cheers guys.

Am in the eastern burbs of Melbourne, well under 500m of altitude I reckon.

Regarding boil off rate, I kept the element in there at 96-97C for about 30 mins (wanted to see if the temp would go higher). What was left was enough to fill a 20L keg king cube (so about 22L as they expand when hot) and all that was left in the keggle was 'dead space' below the tap. Which I also measured as i wanted to know how much this was - came in at a touch over 5.5L.

Roughly then, I lost 2L water in 30 mins which would be 4L over an hour. This would be a boil off rate of about 13% which, from reading, should be ok...I think.

Will keep much more accurate figures during tomorrow's brew session - what's the worst that can happen? Not great but still drinkable beer?

Have another old camping mat on hand which I'll use to insulate the bottom of the keggle and wrap another layer around the outside.

Thanks for the help guys.

AJ

 

[roverfj1200]

My urn 2000w takes some time to get a good boil going. Thermometer reads 98c at this point. How long did you wait for the boil to get going.


Cheers

I got beaten 30min should see it going.

 

[QldKev]

13% is a decent boil off. I would still throw some extra insulation at it. But the numbers look good

 

[Spiesy]

so you only "boiled" for 30mins?

 

[dammag]

A bit OT but if your pre boil gravity is OK can you boil for 60 minutes, losing say 13%, but be adding it back as the boil is happening to retain your original volume?

 

[Spiesy]

A bit OT but if your pre boil gravity is OK can you boil for 60 minutes, losing say 13%, but be adding it back as the boil is happening to retain your original volume?

I'd imagine your pre boil gravity would need to be the same as your post boil gravity if you were to do this... which is kind of weird.

Not sure why you'd want or need to.

 

[Edak]

Make yourself a cheap domed lid, have a look at my galleries to see what I have done with my system.

 

[QldKev]

Also have you calibrated your thermometer? To achieve 13% boil off I assume you would be a bit warmer than 97c

 

[AJ80]

Also have you calibrated your thermometer? To achieve 13% boil off I assume you would be a bit warmer than 97c

No I haven't actually, it is a digital probe type thermometer and I just assumed it'd be ok. The 13% could be inaccurate, I wasn't watching times as closely as I probably should've been. Will get some accurate figures tomorrow.

Have wrapped another camping mate around the keggle which should help a bit.

Bloody excited to be doing my first AG tomorrow though!!

Cheers,

AJ

 

[CosmicBertie]

Have you got a lid that you can use? Or make one....bit of MDF covered with foil. Whack it on whilst its ramping up, it'll heat up the wort quicker. You'll also get a good boil going. Once it starts boiling, take it off.

But, with a 13% boil off, it sounds like you're getting there. Best thing is to try it, ferment it, taste it.

 

[pcmfisher]

Although it appears to be boiling harder, do you get sufficient evaporation with take away containers floating around on the top?

 

[treefiddy]

The boil appears harder because it is. The container reduces the boil surface area, but the surface area that is boiling will boil harder and evaporation will increase in that surface area.
Evaporation provides a cooling effect (think about metho or petrol on your skin).

Even if the overall evaporation rate remains the same, the reduction of DMS will increase because of the turbulence introduced in a rolling boil provides mixing so that it's not just the top that has the concentration of DMS reduced.

I probably haven't phrased that very well, and I did just pull that explanation out of my arse (someone is welcome to correct me) but it's been a long week and I can't be stuffed articulating myself better.

 

[QldKev]

The boil appears harder because it is. The container reduces the boil surface area, but the surface area that is boiling will boil harder and evaporation will increase in that surface area.
Evaporation provides a cooling effect (think about metho or petrol on your skin).

Even if the overall evaporation rate remains the same, the reduction of DMS will increase because of the turbulence introduced in a rolling boil provides mixing so that it's not just the top that has the concentration of DMS reduced.

I probably haven't phrased that very well, and I did just pull that explanation out of my arse (someone is welcome to correct me) but it's been a long week and I can't be stuffed articulating myself better.

It is of the utmost importance that you will remain correct, otherwise bum will be here soon.

 

[bum]

It is of the utmost importance that you will remain correct, otherwise bum will be here soon.

I will be here anyway.

Watching. Waiting.