Back loop only?

[creekbottom]

Patterns always say to crochet in the back loop.  Why can't you use the front loop instead?

[magiccrochetfan]

You can but it looks a little different. Make a swatch of each and you'll see.

[Avon Lady]

If you crochet into the back loop only, you get one effect--the stitch will be in the front.  If you crochet into the front loop, the stitch will be in the back.  If you crochet into both loops at the same time, the work will be flatter.  I hope I've explained this clearly.  GrannySquare, are you there?

[Granny Square]

Helloooo...yes that sounds about right.  Crocheting in the back loop leaves the front loop unused, which forms a decorative or functional ridge.

 

If you crochet only in the back loop in the round, it's decorative, and very slightly less dense than using both loops.  It's also a way to form a base to 'attach' something by using the unused loops.  Sometimes forming a ridge is a way to turn a sharp corner; like if you crocheted the top circle of a top hat, then made the ridge to delineate working the sides of the hat.

 

If you crochet only in the back loop flat, and turning each row, it becomes quite corrugated and is most commonly used for ribbing.

 

Don't ask me why front loop only doesn't make ribbing...I experimented with front versus back long ago, I can't recall the specifics but alternating front and back loop makes different looking textures, and usually a slightly drapier fabric (except BLO flat for ribbing).  

 

edit - it also seems to me that REALLY old patterns (like, mid 1800s) had you working in the BLO for doilies, and also had you work into the chain using the top loop only, which would be the same as the back loop of other stitches.  But really, in modern patterns, I don't 'always' see this except in ribbing or for a special effect.

[Tampa Doll]

Depending on the pattern, you may be coming back to that row to use the front loop for something else.

[redrosesdz]

I have an example of the back loop only effect.  If you open the following link and look at the wings and tail on the Macaw pics, they are done in back loop only.

 

http://www.crochetville.com/community/topic/156646-at-the-zoo-stacking-rings-pic-heavy/