I am an extract brewer and every brew I have done the OG was lower than the intended OG, (my OG is always lower than the recipe's OG). For example I brewed the stout recipe below from beertools.com and my OG was only 1.070 not 1.078. Assuming my hydrometer is accurate and my readings are correct. Could this be caused by not boiling malt extract long enough or steeping the grains for too long/too high temp? What causes OG to be lower than it should be?
Category Stout Subcategory Foreign Extra Stout Recipe Type Extract Batch Size 5 gal. Volume Boiled 3 gal. Mash Efficiency 72 % Total Grain/Extract 11.65 lbs. Total Hops 2.0 oz. 1.00 lbs. Maris Otter Pale info .90 lbs. Roasted Barley info .85 lbs. Belgian Aromatic info 0.60 lbs. Belgian Special B info 0.30 lbs. American Black Patent info 5 lbs. Liquid Amber Extract info 2 lbs. Dry Light Extract info .5 lbs. Candi Sugar Amber info .5 lbs. Dark Brown Sugar info 1 oz. Magnum (Pellets, 14.50 %AA) boiled 60 min. info 0.50 oz. Styrian Goldings (Pellets, 6.00 %AA) boiled 15 min. info 0.50 oz. Styrian Goldings (Pellets, 6.00 %AA) boiled 1 min. info Yeast : White Labs WLP500 Trappist Ale info
Original Gravity Predicted 1.078 Terminal Gravity Predicted 1.016 Color Predicted 32.14 SRM Bitterness Predicted 56.4 IBU Alcohol Predicted (%volume) 8.2 % 96 % overall compliance