Hi
@vintagecoachcollector ! From my research, this is what I understand about vintage
Coach pure aniline leather- the leather is dyed with soluble dyes in vats so that the color goes all the way through giving it a rich color. In order to maintain that natural feel, no protective coating or surface pigmentation is applied. Due to the lack of pigmentation applied, it's prone to scratching, staining and fading.
The leather dye that Ladzuri mentioned - Leather Touch Up Dye (fabulous product by the way!) is a pigmented dye with a sealer built in. LTUD, when applied correctly leaves the leather just as soft and supple as before. I think that's what you are asking - if a pigmented dye will affect the feel of the leather - the answer is yes and no. Yes, the leather can feel different depending on the quality of the product applied as well as the application method. If you go to
Amazon and do a search for leather restorers, a plethora of cheap dyes will pop up.
Translucent liquidy dyes like Fiebings and Saphir do not have a sealer in the dye and unless you apply Resolene, you will encounter dye transfer or worse, if the bag gets wet, it will streak and run. Resolene definitely affects the feel of the leather. It feels stiffer and fake - a painted feel. Because these dyes are translucent, all imperfections on the leather will show through and I think that's another reason why the leather shop recommended using a pigmented dye. The leather is no longer "fresh and new" as it was when it was originally dyed in the vat. The color will not be consistent.
**EDIT**
Totally agree with CA and Ladazuri that Leather Touch Up Dye is incredible! I've used it on a few bags with great success!