Refractometer Readings

[MetalDan]

I Maxi-BIAB so working out my post boil gravity is important to know how much water I need to add to dilute my wort down to the correct OG.I also No Chill so currently I pour the hot wort into the cube, let it chill overnight, then top up with the required water and then add the yeast and begin ferment.

Problem is my gravity readings from my refractometer aren't consistent. For example I might have a reading of 1.068 and add a few litres of water to bring it down to 1.050, do another gravity reading with the refractometer and the gravity is still at 1.068.

Can anything else affect the readings from the refractometer such as hop debris? I cube hop so wondering if all the hop matter effects the refrac reading?

 

[verysupple]

The obvious thing would be that you're not mixing it properly after adding the water and taking a sample that's pretty much all the original wort.

Hop debris will affect the measurement if it's in the light path, but it will just make it hard to read, not change the actual value.

 

[doon]

Are you letting it mix in properly

 

[supertonio]

I calibrate my refractometer with distilled water before use to ensure that it is reading zero correctly. I would also calibrate against a decent hydrometer for extra assurance too.

From what I learn most modern refractometers take into account the temperature of the sample but if yours doesn't then you'll have to take this into account.

I I always find that clear wort in good light will give the best reading possible.

If reading the final SG then using an app such as brix calc can help get final reads right too

If they are accurate they are great pieces if kit and can be easier to use than hydrometers.

Hope this helps.

 

[verysupple]

I calibrate my refractometer with distilled water before use to ensure that it is reading zero correctly. I would also calibrate against a decent hydrometer for extra assurance too.

From what I learn most modern refractometers take into account the temperature of the sample but if yours doesn't then you'll have to take this into account.

I I always find that clear wort in good light will give the best reading possible.

If reading the final SG then using an app such as brix calc can help get final reads right too

If they are accurate they are great pieces if kit and can be easier to use than hydrometers.

Hope this helps.

All very useful information. However the OP stated that after adding water to wort the reading didn't change. That has nothing to do with calibration or corrections or the like. If that sort of thing was the problem, the reading would still be wrong but at least the value would change. So I doubt those are the problem here.

 

[MetalDan]

Thanks for the replies! After adding the water to the wort I throw the cap on and shake/mix thoroughly, which is one reason there's so much hop debris about.How consistent are the sugars in wort? For example if I leave the wort overnight and take a sample from the top, would that be the same as taking a sample from the bottom (i.e. do the sugars drop)?

Maybe on the next brew I'll run the refractometer parallel with the hydrometer and measure off both each time to help troubleshoot the problem.

 

[O-beer-wan-kenobi]

I find my readings can be inconsistent but not by huge amounts.
When I'm getting close to the end of my sparg I like to stop when I get close to my predicted gravity. So I take a couple of readings when I'm getting close to the estimated post boil volume.
These readings can sometimes be a bit high so i take another and then it can be low. And vice versa
When I am done and I'm starting the boil the refractometer and hydrometer readings are the same

I was guessing it was to do with the wort not mixed enough although I do give it a stir?

 

[supertonio]

All very useful information. However the OP stated that after adding water to wort the reading didn't change. That has nothing to do with calibration or corrections or the like. If that sort of thing was the problem, the reading would still be wrong but at least the value would change. So I doubt those are the problem here.

All very useful information. However the OP stated that after adding water to wort the reading didn't change. That has nothing to do with calibration or corrections or the like. If that sort of thing was the problem, the reading would still be wrong but at least the value would change. So I doubt those are the problem here.[/quote]how do we know that his readings are accurate int the first place? If he was adding water then unless the temperature was different this may not have an impact. This was never alluded to in the first place so thanks very much but my answers are valid until refuted by the OP. No need to be a pedant as every little helps.

 

[Online Brewing Supplies]

Have you checked the batteries ?

 

[Black n Tan]

Have you checked the batteries ?

Batteries? Mine must be solar-powered as it just works when I hold it to the sun

 

[supertonio]

Batteries? Mine must be solar-powered as it just works when I hold it to the sun

better reading when facing the sun.......

 

[Online Brewing Supplies]

Mines got batteries and works in the dark.

 

[supertonio]

Mines got batteries and works in the dark.

must be better than mines.

 

[TheWiggman]

Mines got batteries and works in the dark.

*snicker*

 

[Online Brewing Supplies]

Umm well its digital and costs a bit so....

 

[supertonio]

Umm well its digital and costs a bit so....

as with everything in life the more it costs the better it works.

 

[Dips Me Lid]

Hey Metal Dan, are you cleaning the refrac glass in between readings? I usually clean with water and a microfiber rag after a reading, I usually use about 2 drops on the glass and try to ensure there's no air bubbles, I take about 3-4 or readings for my pre boil and take an average of those, they're usually within a couple of points of each other.

I find if I'm topping up the kettle with water it takes a while to see the gravity come down on the refrac, I just keep stirring the crap out of it till I see a drop, I always take a hydrometer reading as well to compare against.

 

[TheWiggman]

Yes on topic...
I have a cheapo unit that I imagine most home brewers use and it has the very simple plastic eyedropper. On the odd occasion I don't empty it completely and can find that the new reading will mix with the old one, giving slightly false results.
More often than not the biggest cause of my false readings is not mixing the wort well enough or not completely cleaning the lens and cover.

 

[verysupple]

how do we know that his readings are accurate int the first place? If he was adding water then unless the temperature was different this may not have an impact. This was never alluded to in the first place so thanks very much but my answers are valid until refuted by the OP. No need to be a pedant as every little helps.

Geez, I didn't say your answers were invalid. Yes, every bit does help. That's why I wanted to get across that while it's good to understand the intricacies of using a refractometer, it was unlikely that those were the reasons for the problem. Is that little bit of info not part of the "every little" that helps? If the OP was confident that they were using the refractometer correctly they could then rule out the effects you wrote about. Doesn't it help to narrow it down?

Also, I thought the temp issue had beed alluded to because of this excerpt and assumed both measurements were at the same temp (although you know what they say about assumptions):

For example I might have a reading of 1.068 and add a few litres of water to bring it down to 1.050, do another gravity reading with the refractometer and the gravity is still at 1.068.

Given that it was stated in the OP that they were no chilling, I assumed the wort had been cooled over night (or howerver they OP does it), a reading was taken, water was added, and then another reading was taken. Tap water temp ~= room temp, hence both measurements were at about the same temp.

 

[MetalDan]

Thanks for the insight into your process Dips Me Lid! Next brew day I'll make sure to take 3-4 samples at each interval and see what kind of range I'm getting. I do clean the refrac after each use but I could do a better job I'm sure, will will make sure to give it a more rigorous clean between each use until I've troubleshooted my current problems!

Cheers for the assistance all