All PVC glues ( most of the white wood glues) shrink when curing, but all tend to cure by water evaporation – Gorrilla glue does not shrink – it expands, as do most polyurethane glues. However these glues cure process is triggered by moisture – very little moisture is needed and is 'consumed' in the process – there is no residual moisture left in the bond, so you would not have a problem with trapped moisture . However…. It can expand 2 to 4 times the applied thickness, bonding impervious surfaces, but pushing them apart…

Perhaps a slow cure epoxy and clamping the boards together, or laying them flat and weighting them?

What is the application?

The factory used to use a contact adhesive similar to evostik, wouldn't want to work in that factory!!!

Styccobond F56 is used by a local flooring company but might only come in the 15litre tubs in their skip. Judging by the smell it is a friend of evostick.

off-topic but the bits of vinyl or whatever they also have in the skip are about 3mm thick and would be a great benchtop covering. It is thick enough for other modelling uses if only they would throw away big bits but is embossed on the top surface with a wood grain.

VHB tape may be the answer!

Although I preferred contact adhesive for single sheets. If I had a lot I often would glue down sheets of formica with PVA adhesive & put them in the door press. I used to buy a PVA from a local chemical company, formulated for the job. But then I would buy in quantities up to 1 tonne at a time, as it could be used for exterior joinery as well.

To speed things up I sometimes added a little water & used a radio frequency gluer to set the adhesive.

Ordinary PVA will do the job, provided it can be clamped & left

Edited By Sam Longley 1 on 30/03/2022 22:20:01

Ask your local hardware store, cabinet maker, kitchen remodeller, handyman etc so you can enter into a two-way verbal conversation. Trying to negotiate your inevitably hyper-specialised needs via the limited discourse of a forum has proven before to waste a lot of members' time on rejected or irrelevant solutions. All it does is generate dozens and hundreds of unnecessary clicks on the site.

For a 100cm x 100cm area, you will need a lot more than the 2 tubes of contact adhesive shown. Use a paint scraper or spatula to get it on fast to get an even coating before it starts to set.

NO NO NO

If that is what you are doing then DO NOT use the titebond as it is designed for one surface to be porus as I said. There will be nowhere for the water content to go.

A contact adhesive spread with a fine notched spreader would be the best option but make sure you get it on evenly as I doubt you have anything to press the sheets together with as any blobs will increase the gap locally and not give you a flat surface. Buy a 500ml can not hobby tubes, something like Evostik 528 or Evostik "Impact" are easy to get hold of

I doubt you are using MRMDF core so make sure the edges are sealed well otherwise the plain MDF core can swell with moisture or even shrink in very warm homes

Only advantage for you of using an epoxy is it is more repositionable than contact adhesive so better chance of getting the edges of the two boards lined up. Your bottles of ZAP would do it.

Edited By JasonB on 31/03/2022 08:47:39

Personally I would start by sanding the two surfaces with something like 120grit paper to give something for the glue to grab onto.

Contact adhesive would be my go to. If the boards sag a little some battons layed across the bottom sheet on the glue do not worry about it sticking as it relies on both surfaces to have glue applied, this will allow you to line up the two boards then remove the sticks one by one and allow the boards to come together once they come into contact it is stuck.

You will need to apply pressure to the boards to really get a good bond so lay it onto something flat and then cover with plastic and place heavy blocks on it as I doubt that you would have something like a vac system, the other method is to have thick battons top and bottom and clamp these the best you can.

Why do I keep thinking the OP is going to use two pieces of ~15mm melamine board stuck together rather than a single chunk of decent kitchen worktop?

I really think the OP is complicating something rather than applying the KISS principle – and will continue to do so, unless we are provided with complete dimensions (ie thickness).

He has melamine faced board which I've only ever seen coated on both sides, if it were one sides it would not be balanced and warp all over the place. I use it regularly and often buy in a ton at a time.

OP would need to buy a belt sander to remove the LPL and as he wants a flat surface would need to be very carful to no sand to different depths, really wants a thickness sander to do it properly.

Bit of plywood would be good enough to throw a cutting mat on top of. Comes any size you want pretty much.