Malt information and usage

I have just started to get into homebrewing and so far I have completed two partial mash kit beers (an IPA and a Witbier). I am trying to learn as much as I can through the internet and books on all the various components of the brewing process and ingredients. So far I have not been able to find a good source of information on malts. Really, I am looking for any and all information regarding malts in general. What are considered base malts and what gives them different characteristics? What are considered specialty malts? How to decide what to use and in what quantities? What is the difference between a 20L crystal and a 40L crystal malt?

As I look forward to starting all grain recipes and continuing on with partial mash kits I want to learn why it is that I am using the grains I am provided and how to choose grains once I do make my foray into all grain. If there are great sources out there on malts then I have simply just missed them. All your help is greatly appreciated! Thanks!

 

I think one of the best sources of information I've found for malts is actually Austin Homebrew Supply. Their descriptions for their grains are very good. As for crystal 20, 40, etc., the number basically specifies the degree of roast and the lovibond number. The lighter roasts like 20 and 40 being very sweet and candy or honey like and the darker roasts imparting more varying characteristics.

 

This might help. Homebrewdad put this together and it is concise and well done. I believe the information is based off Beersmith.

http://www.homebrewdad.com/grain_database.php

 

http://www.beeradvocate.com/beer/101/malts/

https://byo.com/resources/grains

 

the hbt wiki should cover most of the info you're looking for: http://www.homebrewtalk.com/wiki/index.php/Malt

quick rundown to your questions
base malts - pils, 2row, wheat, vienna, munich, maris otter, etc - basically malts with enzymes
specialty malts - crystal, chocolate, victory, and the like
the differences between the malts are generally the time/temp/moisture content they are kilned/roasted at
what to use: bjcp guidelines list common ingredients for the styles. malsters generally list quanties to use and effects. in short, base malt: up to 100%, specialty: <20%
C20 v C40: 40 has darker lovibond, more caramel like character

 

John Palmer's 'How to Brew' as well as Charlie P.'s 'Joy of Homebrewing' both have pretty good basic sections on malts.

 

That is one of the easiest, straightforward breakdowns on malts I've seen. Thanks!