Question about hop weights

[Rasher]

Hi,

I'm thinking of buying a custom made extract kit from my local homebrew shop, to brew a recipe I found online. One of the instructions for ordering the kit confused me and I'm hoping someone could clarify.

It reads: "Please work out the hop weights required based on the alpha acids listed on our website; we will not adjust recipes for alphas."

I know the type of hops I need and the weights for the recipe, but I don't understand the alpha acids part. If anyone knows, I'd appreciate if you could explain it to me.

Thank you!

 

[Clint]

Basically the higher % the less you need to add to get your required bitterness. It don't matter for a dry hop. The sooner you add them to the boil the more you get.

 

[The Baron]

When they give you hops they have a alpha acid % which is used in the recipe and gives you the IBU of the beer(how bitter it is) however hops are grown each year and because they are plants and susceptible to the weather and how the crop grows they will have slightly different Alpha acids each year/crop so you have to adjust the amount up or down in weight to get to the IBU's in the original recipe.
If the Alpha acids are lower you need to add more hops
If the Alpha acids are higher you nee to reduce the amount of hops

 

[Rasher]

When they give you hops they have a alpha acid % which is used in the recipe and gives you the IBU of the beer(how bitter it is) however hops are grown each year and because they are plants and susceptible to the weather and how the crop grows they will have slightly different Alpha acids each year/crop so you have to adjust the amount up or down in weight to get to the IBU's in the original recipe.
If the Alpha acids are lower you need to add more hops
If the Alpha acids are higher you nee to reduce the amount of hops

Oh right, good to know! Thank you