Another stuck fermentation, except I used a starter

[ssf4444]

I brewed a Scotch Ale on july 23, SG 1072. Mashed at 155. I pitched a 1 liter before decanting starter of WLP 028. It seemed to be fine, fermented like a fiend for about 3 days (i.e. good normal airlock activity.)
Well this past friday i was going to rack it to secondary, before so I took a gravity reading...1030...WTF i thought, so I double checked everything, temperature was good, (stayed right around 67 the whole time.) So i spun the fermenter back and fourth to rouse up the yeast....i got a bit more airlock activity for about a day, then on sunday when I took another gravity reading it had dropped to 1029. I really don't call that progress...
A friend of mine suggested that I add some sugar to try and dry it out.
Should I do this, should I pitch another thing of yeast too?
What is the best way I should deal with this?

 

[Yooper]

1.072 to 1.029 is only about 56% attenuation, so it seems like you could go a bit further. It really depends on several things, though. First, the ingredients. If you used a lot of non-fermentables in the recipe, you may not get much lower. Secondly, a mash temp of 155 is pretty high. If your thermometer is off even a couple of degrees, you could have mashed pretty close to 160.

I'd check the thermometer and make sure it's accurate to see if you may have accidently mashed higher than 155. With a high mash temperature like 155, you should have a very full-bodied less fermentable wort but I would still think that it would go lower than 56%.

What was the recipe?

 

[ssf4444]

10# marris otter
3# munich
2# crystal 40
.25# chocolater
1oz roasted barley

I think the thermometer is fairly accurate.
Although i did think of that...
I have brewed this beer several times before and it has always gotten down below 1015

 

[TipsyDragon]

well im pretty sure the Crystal 40 and chocolate are unfermentable. like Yooper said the high mash temp will make a less fermentable wort. thats why AG brewers calibrate their thermometers. boil distilled water and see what temp your thermometer says. i'm willing to bet it won't say 212F. do the same with freezing water. put a bowl of water in the freezer and come back every half hour or so and break the layer of ice on top. when its mostly slush take it's temp. after that its simple math to figure out the correction factor for the thermometer in question.

 

[beowulf]

In addition to the terrific comments above, I would think that a 1L starter might be a bit lean for a 1.072 beer. If a 1L starter has worked in the past, then possibly something else...insufficient aeration, perhaps?

Also...not to be irritating, but there are legions of posts already out there on the topic of stuck fermentations. A quick search should yield plenty of ideas on what to try next.

 

[babalu87]

In addition to the terrific comments above, I would think that a 1L starter might be a bit lean for a 1.072 beer. If a 1L starter has worked in the past, then possibly something else...insufficient aeration, perhaps?

Also...not to be irritating, but there are legions of posts already out there on the topic of stuck fermentations. A quick search should yield plenty of ideas on what to try next.

This, its actually way small even if the yeast was SUPER fresh