"What is the purpose of the leather/vinyl treatment?" In your case, the purpose may well be to preserve the object just as it is. For others, the purpose might be to rejuvenate the leather to be more supple. For that, the products needed might be quite different.
Here is my process and goal when refinishing automotive leather. It is simple: Clean, Feed, Finish. In detail, and this is long...
- Carefully clean the surface of the leather without flexing it too much. Old leather is dry and cracks easily. This is because the natural oils and fats have evaporated from the leather fibers. (Okay, at least the volitle components of the natural oils and fats have evaporated.) When the fibers break, cracks form -- then tears. Also, Connolley leather is not vat-dyed. Rather, it is 'painted' with lacquer. That is why the leather in (older) British cars feels hard, shines and shows surface mars so easily. The surface is all that you see and all that you can get to. The inside of the leather is unreachable! It is sealed by the lacquer and never gets any of the treatments that we lavish upon it.
- Saturate the leather with a high-colligan leather treatment to rehydrate and strengthen the fibers. This does not get to the inner fibers (for the reason described above) but it DOES get into the fibers in the cracks where the leather is already damaged. The goal here is to minimize the potential for damage while further treating the leather. I use Leatherique's Rejouvinator Oil. (No commencial interest in the product or company.) Avoid, like the plague, any treatment containing silocone.
- Strip the old lacquer off of the leather with small amounts of lacquer thinner. This is a violent process so you see the need to feed the distressed leather first. Use lots of paper towls to wipe away all traces of lacquer as this stuff is the seal that has prevented you from feeding the leather all along. Allow to dry for a day (or a few hours). Re-examine the leather for traces of the old lacquer. They will be obvious once the leather is dry. Spot clean, as needed, and allow to dry again. At this stage, the leather is 'open' and easily damaged as the lacquer thinner has stripped away some of the oils from the surface of the leather, especially from where the lacquer was still impermeable. Handle with care avoiding excessive flexing.
- Saturate the leather with Rejouvinator Oil. If the weather is hot, it also helps to cover the applied area with plastic wrap to keep the fats from evaporating too quickly (allowing more to be absorbed into the leather fibers). I do this process multiple times over two or three days. You will notice with even after the first application that the leather is MUCH softer. That is because the fibers are flexing easily and not breaking! Continue this process until you are satisfied that the leather has absorbed all the fats that it can absorb. I just can't put into print how much of an change this makes in the leather. Old boots versus new driving gloves perhaps?
- Clean the surface of the leather with a very light washing with soap and water. The goal here is to remove any fats that are on the surface, not to clean the leather. This is the 'prep' stage to refinishing.
- In any project, it is hard to cover dark colors with light colors but it can be done. It just takes more time and more coats. The leather will be 'funky' looking now as it has no finish on it but does have lots of staining from bits of the original lacquer soaking into the leather. Do not dispair.
- I use Leatherique's dye to finish the leather. It is NOT a dye but rather a surface finish not unlike what Connolley used -- except that this new product is water based. It smells like latex paint and I would be surprised if it didn't have a latex base. It can be brushed on, rubbed on or sprayed. I always spray it. It is NOT like anything painters are used to as it is water based and dries VERY slowly compared to solvent based paint. If you put it on like regular paint it will all run to the bottom like Windex on a window. The first few coats need to be applied just as a mist or a dusting and allowed to dry for some time. Subsequent coats adhere better as some of the moisture in the finish is absorbed into the underlying finish. Again, very thin coats are needed. I typically will use 10-15 coats with the final coat just thick (wet) enough for an even surface appearance. Allow the final job to dry for a day or two. Please don't rush this step. The finish has to cure.
- At this point, the surface is pretty much resealed making it really important that you took all that time to get the underlying leather in top shape before finishing. How long did the original finish last? Quite a while. With 'healthy' leather underneith, this finish will last a long time also -- and look great.
I have pictures along the way on various seats, panels, etc., from the Ferraris that I have restored. I also have used the Rejouvinator Oil on my BMW M3 but as the seats are black, redying has not been needed. This is also my daily driver and the goal has not been to make 'new looking' seats, just soft seats that are not being damaged by daily use. Anyone wanting to see some of these pictures, e-mail me privately.
Again, I have no interest in Leatherique but I do use their products exclusively now. I hope these comments, however long, have helped some of you.
Best regards, Rick
[Ed Note: LEXOL is also a highly recommended product, and can be found at many horse & rider supply stores.]