That glue used, judging by the color, is called Dap Weldwood Trim & Landau Adhesive.
...and there certainly wasn't enough used. Especially for a non-headliner type material. That fuzzy backing can cause probs when an insufficient amount of glue is sprayed.
I can also see that there's just been a quick light coat applied. Certainly not enough & haphazardly, too. The glue is yellow & it should be a solid color across the whole back of the fabric. It needs to applied in nice even coats. Like painting a vehicle. Each pass of the spray pattern should cover 50% of the previous one.
Both the foam & the fabric need to have a coat of the glue.
I'd be giving both at least 3 dustings of the glue. The first being the lightest. This helps to prevent the following coats of glue from soaking through to the fabric's face.
The 3rd go with the glue can be a fair bit heavier than the first.
Each time a layer of glue is sprayed, it must be allowed to flash off & become dry to the touch.
The glue itself is held in suspension in a solvent base. As it flashes, it breathes off the solvent. Try glueing stuff together before the solvent dissipitates & that gas gets trapped between the layers of the fabrics.
This will either cause bubbles or complete failure of the bond.
Once the two fabrics have been stuck together, they must be rolled with a hand roller. This what creates the near permanent sticktion. This is important!
No panel with any type of fabric/vinyl/leather leaves my shop without being rolled first.
Just sticking things together by rubbing by hand will not guarantee that the glue will hold. Especially with a headliner, where it's only the glue itself that is suspending the weight of the fabric.
You can do this at home. There a couple of different glues available at most home improvement stores that are acceptable.
3M '76' or 3M '90' I prefer the '90'. Stronger formulation. The '76' will still work, though.
It's not cheap. Last can I bought was over $35.00(cdn.)
Use it in the same manner as previously described.
When I do use this glue, I like to do the first coat across the material & H/L panel. The second, coat 90* to that first one. Up-n-down. 3rd. & fourth at 45*.
Light coats!
The 3M glues have a tip that not only have the ability to be twist the fan pattern of the glue in any direction you want, but are also infinitely adjutable from Low to High.
This is one type of roller in my toolbox. This is the one I'd recommend for an H/L. Medium pressure. You don't really need to lay real weight into it to create a good bond.
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