How are you sterilizing the bottles???? if with heat..... let the bottles cool you could be killing off the suspended yeast. If chemically rinse, rinse, rinse again. Also, try a few batches using 1 1/4 cups of dry malt extract instead of sugar. Also make sure all of your bottling equipment is clean and operable.... replace any plastic thats dented or scratched.... thats about all I can offer I hope it works out... I know the frustration

Carbonation has several variables.

1. Racking time. How long was the beer aged before being bottled and the type of yeast used in fermentation. Some yeast settle out faster and consequently less yeast in the bottle means less carbonation (or it just takes longer).

2. Yeast viability in the alcohol. Again, certain yeast tolerate higher alcohol better

3. Beer temperature. This can go both ways. Carbon dioxide will dissolve more readily in colder beer so chill before you drink. And, warmer temperatures cause yeast to multiple faster. So keep the beer at about 70F for several weeks after the priming and bottling. Of course, too warm will wipe them out.

4. Clean bottles. Clean means sterile AND free of cleaning substance residue.

5. Unclean batch. Beer contamination in the fermentation. Some molds secrete toxins that kill yeast (kind of marking one's territory).

6. Cool the primer. Priming mixture was added to the beer while too hot. I know this is a stretch but you'd be surprised how many people figure that a little hot water won't due any harm.

7. Check your equipment. Bottle caps not sealing properly. Different equipment doesn't always work the same. Again, a stretch but it's covered here.

8. Type of beer. Some beer takes carbonation more readily.

9. Wait longer. Six weeks is awhile. But, some yeast (especially lagers) just take longer.

10. Stay dark. Bright light (especially sunlight) will kill yeast.

That's all I can think of right now. You could always go to kegs, instead. Much easier!

You probably already got answers, but here's mine anyway. The short answer is that all things being equal, the amount of priming sugar affects carbonation. But of course the recommendations is to use less priming for a keg than for bottles. I just bought some of those mini-kegs (5L) from Gene, and am trying them out for the first time. The article he gave me stated an incredibly low amount of priming sugar--much less than the normal 3/4 cup per 5 gal. used for bottles, or 1/3 to 1/2 cup for large kegs.

Some say that the final gravity should be taken into consideration--use more sugar for lower final gravity beers, on the theory that there is less residual fermentables in the beer. Someone said that at a meeting, I haven't read that anywhere. It might be true--it doesn't really make any sense to me--but what do I know.

I get a firmer head when I either don't let it ferment out till it appears dead (one bubble every several minutes). Also, I rarely use corn sugar for bottling, I prefer using light DME instead. Fore every 1 cup of priming sugar called for in the recipe, I substitute 1 1/3 cup DME. The DME gives it a much firmer and long lasting head.

Are you aerating the wert before pitching your yeast for fermentation? If you've boiled the wert, and haven't added oxygen again (when below 90 degrees), then the yeast may be mostly dead by the time fermentation is done. A well shaken wert always has a longer kick to it for me.