First AG - and massive calamity...

[Hoppyland]

damn these really smart people who know way more about this than me.

Whoah! I bet there's plenty that you know that I don't!! :)

 

[GHW]

Whoah! I bet there's plenty that you know that I don't!! :)

I seriously doubt that but don't worry I'm just being a pillock.

Taking the thread sideways though, does the proportion of fermentable/unfermentable sugars in the wort make no difference to gravity?

 

[Hoppyland]

Taking the thread sideways though, does the proportion of fermentable/unfermentable sugars in the wort make no difference to gravity?

My understanding of OG (and FG) is that they are both measurements of what's called "Specific Gravity" which I'll call SG. SG is a measurement of density, with particular reference to water. Distilled water has a SG of zero - or 1.000 as measured by our hydrometers. If you dissolve any solid material in the water it increases the density. (Think of the Dead Sea, where you can float without swimming).
But ordinary seawater is a good example. I think it has a SG of about 1.025 (Damn, I'm a retired marine biologist - I really should do better than think)
Of course, it's completely unfermentable, being mostly common salt dissolved in water.

Back to your question: I would guess that the proportion of fermentable/unfermentable might make a difference to OG. But only on the theoretical grounds that unfermentables are bigger molecules, therefore heavier, therefore likely to increase the SG.
When it comes to FG, though, there will be a really detectable difference - for the obvious reason that the fermentables will be gone (CO2 gas given off, ethanol produced: and ethanol is even lighter than water) whereas the heavy unfermentables will remain, and will do their best to propel your hydrometer upwards & out of the water!

 

[GHW]

My understanding of OG (and FG) is that they are both measurements of what's called "Specific Gravity" which I'll call SG. SG is a measurement of density, with particular reference to water. Distilled water has a SG of zero - or 1.000 as measured by our hydrometers. If you dissolve any solid material in the water it increases the density. (Think of the Dead Sea, where you can float without swimming).
But ordinary seawater is a good example. I think it has a SG of about 1.025 (Damn, I'm a retired marine biologist - I really should do better than think)
Of course, it's completely unfermentable, being mostly common salt dissolved in water.

Back to your question: I would guess that the proportion of fermentable/unfermentable might make a difference to OG. But only on the theoretical grounds that unfermentables are bigger molecules, therefore heavier, therefore likely to increase the SG.
When it comes to FG, though, there will be a really detectable difference - for the obvious reason that the fermentables will be gone (CO2 gas given off, ethanol produced: and ethanol is even lighter than water) whereas the heavy unfermentables will remain, and will do their best to propel your hydrometer upwards & out of the water!

No Dead Sea porters to be brewed then.
And you definitely know more about this than I do.

 

[Cwrw666]

If people are using glass thermometers, remember that most of them are partial immersion type and are only accurate when dipped into the liquid to the correct depth of immersion. in the case of mine it is 76mm. If you dip it deeper than that it reads higher than the true temperature and if you dip it in less it reads low. Most thermometers have a mark on them showing how deep to insert them. If not, it will be printed in numbers on the side.

I wrote an article on this a good while back.

http://www.thehomebrewforum.co.uk/showthread.php?t=54435

I had a lot of confusing readings with it showing like 104C when the water was boiling and also high and low in iced water depending on the depth.

I have a cheap ebay digital thermometer and it works great as long as:

1. I keep the electronic bit dry.
2. I only insert the first 10mm into the fluid.

If I insert my digital thermometer to different depths I also get inaccuracy like the glass ones. This may account for some of the problems listed above about digital thermometers not reading true. Try experimenting with dipping the tip to different depths in boiling water and see where it reads true. Then stick to that depth of immersion for accurate readings. Mine works true at 100C and 0C (iced water) if I insert it to the same depth, The difference is about 0.25 of a degree C which is plenty good enough for accurate mash temperatures.

Dairy thermometers are designed to float in the liquid at the correct depth so depth of insertion isn't an issue if you let them float freely.

 

[Tony1951]

Dairy thermometers are designed to float in the liquid at the correct depth so depth of insertion isn't an issue if you let them float freely.

That would be useful. Milk probably has a different specific gravity than beer though, so they won't float at the correct level in the amber nectar I would think. Mash is another matter too, probably. Of course as long as you know what the correct depth is, you can mark the glass tube and stick it in at that depth.

Fortunately, we can all get away with a whole pile of errors in making beer and still turn out delicious beverages, which is a great attraction of brewing. I doubt that any of my brews are done the same way twice when it comes to exact weights of ingredients, temperatures and most other variables.

:)

As an example of that, today I al bottling an IPAn that stopped at above 1016 because I was trying to get a good mouth feel and got the mash slightly hotter than I probably ought to have done. I got into the ballpark I wanted, but over did it a touch. It tastes good though and will probably finish up with a pretty rich taste and feel about it.

I'm going to brew another batch of the same sort tomorrow and will try harder to get everything just right by measuring EXACTLY on the quantities and temperatures. There are quite a lot of variables to get right though in aiming for a 68C-69C mash. I think my last one was probably nearer 70 because I assumed that 12 litres was 6kg of grain. I now have a good set of digital scales so will get nearer maybe.

 

[VillageBrew]

Hi,
Not sure if your digital thermometer is similar in design to mine but I have also had problems half way through a brew day where my thermometer began reading ridiculous temperatures. Mine is a cheap digital thermometer with a probe connected via a wire (from eBay). I was able to repair mine by disconnecting the probe from the thermometer and placing the stainless probe on a baking tray in the oven at 200C for 30 mins (you need to leave the wire hanging out of the oven). After 30 mins I took it out of the oven and could see sugary liquid had bubbled out from the connection between the probe and the braided cable. I let it cool down to room temperature before testing and it has worked fine since.
Hope this helps

That has worked a treat! After reading some of the learned commentary on here I'm not certain how accurate my thermometer is but the 22°C it is reporting in the kitchen feels more accurate than the 94°C it was claiming earlier.

Huge thanks to BrewzLee. :thumb:

 

[BrewzLee]

Excellent, I'm glad it worked for you. Mine now reads within 0.5c of my other digital thermometer after the repair so seems to be accurate. The important thing is to prevent the joint between the stainless probe and the wire from being submerged in water/wort as this is what causes the inaccurate readings.:thumb:

 

[Hoppyland]

And you definitely know more about this than I do.

Don't you believe it! As examples: Wort chillers, not a clue. Never tried one. Fermenting lagers? No idea - don't care for them, as I only brew "English" style beers. BIAB? Never tried it, my knowledge = zero.
I could go on for a very, very long time here, I think!
There are a few things of which, with my background, I feel I have a really good grasp. There's many, many other aspects where I'll just flounder
One of the great things about home brewing I feel - there are so many ways to approach it, and so many of them work well!