Gluing Overview
Thickness of Glue
Glue needs to run of the brush, if it is too thick it will go on too thick and will not spread nicely and won't stick properly as it won't soak in very well and will just “sit” on the surface. Glue for patching can be slightly thicker.
Gluing soles
Put plenty of glue onto the brush then start in the middle and lay it on evenly, avoid over brushing (that’s where you brush or try to brush the glue around and its already starting to dry, often as the glue is getting spread too thinly). Always glue shoes then heeling and/or soling products. As the shoes are more likely to need two coats and it reduces the risk of getting glue on the shoe as you get them out of the way sooner. Let glue dry for approx. ½ hour, and then reapply to those surfaces needing two coats. Leave to dry for another ½ hour, before assembling.
Here’s the basics, are either of the products synthetic?
If yes, Clear Glue, so now is it TPR? If so use TPR primer on the TPR only, if there is doubt as to what synthetic product it is wipe with solvent, then let dry for 15min then glue with Clear Glue, otherwise just use Clear Glue. For everything natural (leather/wood/rubber/cardboard/eva) use Yellow Glue or for heels ATOM.
How do you tell them apart? It is often easier to think of what it is not, as this will narrow your choices
down; Tricky ones are PU Foam, PVC/Vinyl (Poly Vinyl Chloride) and TPR (Thermo Plastic Rubber)
PU Foam
Think Rieker, John Bull(Dual Density) it rots, it splits, absorbs moisture, grinds powdery when new and
then melts when older, has little air bubbles on the outside which are more visible on sharp
corners/edges. Often has round holes in the heels and maybe shallow grooves across under the fore foot,
you can’t usually see the holes from the bottom of the sole, only once the upper is removed, maybe you
will see the heel holes from the bottom once you have ground a lot away.
PVC
Think Doc Martin, (greenish sole with Black randing) it wears smooth and shiny, comes in many densities
TPR
Think Budget cheap nasty, but often used on expensive as well. Flicky when ground, often has air bubbles, in a bit from the edge, often has square holes in the heels and support lines across at the front, only visible when badly worn or once you have ground a lot off. Use primer. Use less heat on the TPR and maybe a bit more on the sole. If you put solvent on to a rag and wipe black TPR, the rag will become black.
For all the above materials it is best to follow these 6 steps:
1. Always grind both surfaces thoroughly and dust off well.
2. With plasticized materials such as PVC clean the greasy surface with thinners if you have any doubts about getting it to stick.
3. The softer the material, the less pressure that is needed, but pressure is needed for longer
4. Materials must be totally dry
5. Let glue dry before reheating
6. If in doubt let sit for 30 minutes before grinding
Which glue
Natural?
Yellow glues. Bostik 1222, Ados F2, Renia Ortec.
Synthetic?
Clear glues. Bostick 999, Ados F3, Renia Syntic Total.
TPR?
Use Renia yellow primer.
Looks dodgy?
Wipe with solvent .
Pressure
1 - 5 bar depending on the material
1 bar min 60 sec
2 bar min 45 sec
3 bar min 30 sec
4 bar min 15 sec
5 bar min 10 sec
1 - 1.5 bar for soft materials or air cushion soles.
Don't deform materials during pressing,
otherwise the adhesive film will be destroyed.
Clear Glue
Bostic 999 Reactivation Temperature: 70 - 80°C approx.
Renia Syntic Total 40°C seams to work fine
Open Time: Short. This means it doesnt have much of a window of time where its set enough to assemble and that it's still active enough to bond.
Yellow Glue
Yellow glues. Bostik 1222, Ados F2, Renia Ortec.
Drying Time: 5 - 30 minutes, depending on the materials and room conditions.
Open Time: a) Contact cold bonding: 20 - 90 minutes approx.
b) Heat activation bonding: exposure to adequate thermal activator (infrared,
flash etc.) till 40 - 60°C, after cold contact open time has been exceeded.
Issues
Heating for 1.8 makes the existing soles come undone, use less heat on next shoe. Usually best to pull the one that came unstuck right apart, clean out the old glue and re glue. Sometimes atom will work or just pressing while still hot.