Hi All,
I picked up some espresso coffee at a local roastery.
I had them grind it to "espresso" grind for me.
Upon arriving home I find that it isnt fine enough.
Can I grind again to a smaller grind?
Also is there like 12 beans to a double shot or is there a rough number to load in the grinder?
Thanks from a newbie!
All the best,
Wayne

No!

Don't put ground coffee into your grinder! As far as I know, this will leave you with a big mess and possibly a damaged grinder (maybe not damaged, but it's certainly not designed to grind grounds, only whole beans).

Now that I reread your post, I'm a bit confused: if you have a grinder at home, why get the beans ground at the store? What kind of grinder is it? (If it is a blade grinder, you could probably grind the grounds again, but at that point you're taking stale* coffee to an inconsistent grind level which will likely still not work for espresso, and if it does once, you'll probably have trouble getting it to the exact same grind again.)

As for the number of beans, most people dose by mass. Each type of bean (and roast) has a different mass and therefore for the traditional 14g dose each coffee will have a different number of beans. A scale is a great tool for starting out, or you can slightly overfill your basket and sweep a finger across the top to level, and then tamp. This should give you a pretty good starting ballpark.

*Stale is an assumption: if it's store ground and it's been longer than an hour or so...

Dan,
Thanks for the input. I am in the process of getting an used Rancilio Rocky.
Thanks for saving me from damaging my grinder!
So that is why I had the roastery grind my coffee for me.
All the best,
Wayne