Very Low Finishing Gravity

[dukeellington]

General question to see if this theory is realistic, after I've had a few problems with my last couple of brews.

Basically I've ended up having three brews finish very low. I'll give the details:
1. Saison (Partial extract), WLP530, Mashed for 90mins at 63 - 67C, OG 1.066, FG 1.002 (in bottles - half gone)
2. Tripel (all grain), WLP570, Mashed for 90mins at 64 - 66C, OG 1.064, FG 1.000 (bottled today)
3. Irish Red, WLP004, Mashed for 90mins at 64 - 66C, OG 1.004, FG 1.000 (still in fermenter)

What's happened was I did the saison, its a recipe I've never properly been able to repeat since I got a great beer out of it years ago, so when it ended up at 1.002 and fairly tasteless I said fuck that recipe I'm never doing it again (and for shame I threw 40g of mosaic in for 48hrs before bottling) and moved on.
Did the tripel next and was really happy with it when I took my first gravity reading (it was around 1.018) but a few days later it was down to 1.000, I was beginning to worry about some infection carrying on the ferment, although flavorwise I couldn't taste anything bad, except some bitterness and the star anise overpowering. I put this down to no sweetness to balance out hops and spice.
Before the tripel had finished I had already brewed the Irish Red, and I've just taken the first gravity sample and again its down at 1.000. This time I actually think it tastes really good, but again FG much lower than expected.

So the worry in my mind is obviously infection, and of course everyone is sensitive to suggestion that their hygiene isn't perfect, and I'm no different so I obviously bias, but I think I'm okay, aside from the saison (and even then the late dry hop makes it passable) none of them are ruined flavorwise even if they don't quite taste exactly as expected. Also all three of my buckets get dosed with oxi post cleaning, and then star san after that.

Just this evening something dawned on me though - not long before these batches I switched from a laser thermometer to a thermapen one which I assumed would be more accurate, but perhaps it's reading low? So i checked it against my inkbird thermometer (also a new addition) and sure enough it reads 1.0 - 1.2C lower (At 18C)

My question is would this ~1C difference at mash time be enough to lead to the overly fermentable wort? For reference I mash in one of those picnic box jobs, and always give it 90mins, checking the temp every 30 mins.

Apologies for the long spiel, just wanted to get the details on the table - any advice appreciated.

[Hingo]

Just mash higher - 67°c and ~74°c out

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[DEMPSEY]

Are you reading your hydrometer correctly

[pob]

There's quite a difference between 63°C and 67°C, i.e. your saison. You would expect to have a lot more fermentables at 63°C than at 67°C and with a possible over-read of a further 1°C that will add more (& reduce body).

Worth doing a proper calibration of all your thermometers (ice slushy method) - just because its new, doesn't necessarily mean it's accurate (although you would expect it to be).

If you can't readjust them, just take a note & write the correction required on a sticker on it for future use.

[pob]

Also, per Dempsey check your gravity readings.

Make sure you replace any plastic gear you reckon could be infected , its cheaper now than after binning a couple of batches you thought were ok but now have a doubt.