The affect that different chemical treatments have on fabric is too broad to discuss in one post. For simplicity's sake let's look at the dyes and printed (localised dying) components of quilt fabrics.
Cotton fibres go through an enormous number of steps between the humble cotton plant and the quilt fabric shop. There are special machines that remove debris, brush, burn, spin, dip and weave. Chemicals such as starches and resists are applied then washed off.
Starch or starch like chemicals are used to help fabric retain shape while being processed. If an inexpensive fabric feels stiff, this is usually starch, not dye causing the stiffness. Washing fabric may make it feel more supple.
Most quilting cotton fabric begins as an all over colour. (plaids are the notable exception here). Plain, single-coloured fabrics are created using dye baths, submerging the entire fabric in a solution.
Printed fabrics are just that. Plain coloured fabrics are printed using computers, screen-printing, stencils, wooden blocks or some variation of a printing technique. Entire books have been written on this subject, so I won't even attempt to be too specific here.
Dyes or pastes are used to create patterns on the fabric. The dyes are set using chemicals and heat.
This is where some disappointments may occur. If dyes are not properly 'set' they may migrate when washed. The last thing a quilter wants is to see their beautiful creation marred by dye that runs or bleeds.
All fabrics that are going to be used on laundered quilts MUST be pre-washed. Test for colourfastness by soaking fabric in hot water with a small piece of white cotton fabric. If any colour migrates, wash repeatedly. If washing repeatedly does not resolve the problem, either reject the fabric or use Synthropol to remove excess dye.
***Yes, you may try the salt or vinegar solution: just be aware that depending on the process used, you may set the dye or strip it out of your fabric.
Another issue the may occur with fabric colours is most frequently seen on inexpensive novelty fabrics. Most dyes and pastes permeate the fibres. The fibres are still clearly distinguishable and supple.
Some popular or novelty fabrics apply a thicker dye or paste that leaves a surface layer. Gold and silver are often used in this embossed typed of fabric although the 'paint' may be any colour.
Look carefully before purchasing these fabrics. If a colour is proud of the fabric, sitting on the surface of the fibres or seems overly smooth and rubbery, it can and will wear off if exposed to repeated friction or rubbing.
These fabrics are suitable for art quilts or wall quilts but may disappoint on bedding. From experience, I can state that heavily painted fabrics look truly worn before the fibres, creating a tired looking quilt. Avoid using large blocks of heavily painted fabric on bed quilts.
With the embossed type of fabric, bear in mind that the heavier layer will add resistance to a needle when hand piecing or hand quilting.
The old adage of 'you get what you pay for' definitely applies to the way dyes and prints may affect your projects!