Why are seams pressed? (Not ironed. Right?)
Ironing might stretch the block at the seam especially if seam is on the bias. Also pressing before the seam is pressed to side or open sets the stitches and will make the block lay flatter.
Press light fabric toward dark fabric?
Pressing dark to light causes shadowing of the seam and distorts the appearance of the block design.
Press heavier fabric toward lighter weight fabric?
Have never heard of this. the opposite appears more realistic to me. However, pressing heavier toward lighter does not require a fold in the seam line of the heavier fabric and might enable the block to lay flatter.
At which part of the assembly do I press?
Some books recommend after every step. Says it makes the entire block lay flatter and be more accurate.
Is there a standard? - No there is no standard.
Is there a strong recommendation? - No, whichever works best on the piece you are doing.
Does the standard and/or recommendation change depending on the pattern being used or the teachers preference?
- Probably on the teacher's preference. Some teachers/books etc are adament about doing it "my way" but I believe the way depends on the individual quilter and what works best. Same with pressing seams to side or open. I do whichever makes the top side of the block look better and is easier for me to complete.