The Best Edge Paint Primer...?

Edge paint primer is a weird thing, it’s use on leather edges varies from brand to brand.

Stahl Base 427 I’ve found has to be used alongside a primer to work properly especially on chrome tanned leather.

I remember applying Stahl to a cut edge around a zip on a pure chrome tanned laptop case I was working on. The next day I noticed a small part had come away so I pulled on it and the whole thing came away in one! Replaced with Giardini - no more issues. Binned the Stahl.

On the other hand, Uniters primer according to my distributor is used for leathers that tend to reject anything water based, such as oil tanned leathers, English bridle leathers or any other types of leather resistant to water.

Strangely, each and every time I’ve tested the primer, my favourite Uniters EP2000 is stronger WITHOUT it (you may remember the tests I conducted on an Instagram live a few months back).

Uniters EP2000. 3 layers of paint over primer peeled off mechanically from English Bridle:

But, It appears that EP2000 with primer, is slightly better on difficult leathers than without, but for most leathers that aren’t high in oil/wax, EP2000 is more tenacious by itself.

Now for those of you who have watched ‘The Making Of Luxury Watch Straps’ video series, you’ll know a trick to improving the effectiveness of Uniters primer. The primer in this case is because the cut edge of the watch strap exposes reinforcement material which edge paint is not designed to stick well to and the primer acts as a better adhesive here.

Uniters primer is basically water based clear acrylic adhesive (side by side comparisons show identical effectiveness in every way to standard acrylic adhesives) and edge paint doesn’t stick to acrylic plastic very well, BUT it sticks to the acrylic plastic better than oily/waxy leather (stay with me).

So, Uniters primer is simply a compromise for difficult leathers.

So what’s the point of this post? Well, I wanted to find a primer that works on difficult leathers that gives the same strength to EP 2000 as it has by itself on ideal leathers.

The answer it seems has been under our noses for quite some time!

Edge paints are water based polymer emulsions that include adhesives, drying agents, matting agents, UV inhibitors amongst other ingredients, but I have always had a sneaking suspicion that they contain a synthetic rubber for flexibility..

Enter Saregum.

Saregum is a solvent free contact adhesive based on synthetic rubber in a water based emulsion. Sound familiar? Hmm.

So, I mixed Saregum with de-ionised water to get the consistency just right whereby it soaks into the edge of leather, bonds with the fibres, yet leaves the surface without a thick layer on the top so that there is enough surface area for the edge paint to grab (like sanding, but here you don’t need to).

The result? The edge paint and leather is destroyed if separation is attempted mechanically.

Confused? Don’t be:

Put Saregum into a small applicator bottle. ⅓ Saregum to ⅔ de-ionised water.

Shake vigorously until mixed.

Apply using the metal spout to your leathers cut edge.

Wait half an hour (about the same time as it takes to watch my awl sharpening vid!).

Apply your edge paint as normal.

Carry on living your life.

I hope this helps guys, but don't forget to experiment for yourself before using this technique on any of your products.

Now, I'd like to hear your thoughts and experiences with primers!