Too long in FV? Powdery off taste

[skipper]

I brewed the following 3 weeks ago:

2.3 kg pale malt extract
0.4 kg crystal malt
pacifica hops for bittering
riwaka/willamette for flavour

1.043 sg. I used s04. After one week fermenting i took a small test amount and checked the hydrometer reading. It was 1.012 and tasted lovely. fruity and hoppy and exactly what i was expecting. I then left it for another week as i have been leaving all my extract beers 2 weeks recently and found this has made great beers. When i took a small test amount on bottling day the hydrometer reading had remained the same. however, now when i tasted the beer it had a strange metallic/dry powdery flavour. I thought i might as well bottle it and having done so, after 1 week in the bottle, the flavour was much better (drinkable) but there still remains a strange off taste. you drink the beer and then about a second later this flavour appears which is like a sort of dry powdery after taste. it is relatively subtle but irritating. after 3 weeks it is still there and I get the feeling it isn't going anywhere - it isn't getting better week by week.

anyone got any ideas what may have caused this? i can't see i did anything particularly different than before. Why would the flavour not be there after a week in the fv but there after 2? The only thing I can think is either it was left too long (but i usually leave beers that long and this seems common) or some kind of infection was introduced after a week (but i sterilised the trial jar well and the beer isn't vinegary). The only other thing which was different is that i was using a rubbish ceramic hob which had difficulty boiling the beer and some of the time i half put a lid over the top to get it boiling (but it tasted good after a week so i can't think that this is the culprit).

[EoinMag]

Powdery, sounds kinda like astringency. Not all infections taste sour....

Did you steep your grains, and if so, how?

[skipper]

yes i did, steep in 64c - 68c water for 30 mins. i've never had this flavour before and i always steep the same way

[EoinMag]

Palmer says probably astringency from a steeping problem:

Astringent
Astringency differs from bitterness by having a puckering quality, like sucking on a tea bag. It is dry, kind of powdery and is often the result of steeping grains too long or when the pH of the mash exceeds the range of 5.2 - 5.6. Oversparging the mash or using water that is too hot are common causes for exceeding the mash pH range. It can also be caused by over-hopping during either the bittering or finishing stages. Bacterial infections can also cause astringency, i.e. vinegar tones from aceto bacteria.

http://www.howtobrew.com/section4/chapter21-2.html

[skipper]

as a happy update on this i had a bottle the other day and it tasted good. the off taste has gone and the beer is nearly in condition. interestingly suddenly the hop aroma has really appeared. it seems to have taken a long time for this beer to condition - 5 weeks in the bottle. maybe the powdery flavour was astringency from over hopping (beersmith said 31IBU from 135g of hops - most added late - so i doubt it was this) or steeping the grains. maybe it was from the yeast and this has settled out of suspension or improved over time. perhaps the ceramic hob rubbish boil has lead to needing more conditioning time.

whatever it was, giving it a long time conditioning seems to have sorted it