Gluing the 'backside' of masonite?

[Chris Padilla]

I need to make 4 closet doors from 2. These closet doors are original to my mid-70s built house. They appear to be 2 sheets of 1/8" masonite glued to a solid wood 3/4" frame along with cardboard Xs as needed throughout the sandwich. They are basically a torsion box.

Anyway, the backside of the masonite is that brownish, rough surface that I'm not sure what kind of glue might stick to. I need to glue in some support plywood so that I can then have a solid surface to glue an 1/8" strip of poplar along to give uniform and strong edge to the cut door.

What kind of glue do I need? PVAs work? Epoxy better? This stuff ain't wood so I dunno what glue might work to stick to it. I wonder what the door manufacturer used.


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[Mike Schuch]

I would go for a polyurethane (Gorilla) glue. When the glue expands it should fill in all the little gaps to get a good grip.

You might also try a polyurethane construction adhesive (liquid nails).

[Jerry Miner]

PVA works fine for this. (Gorilla glue would work, but it's messy)---Masonite may not be wood, but it IS wood fibers---glues like wood.

[Bill McNiel]

I agree with Mike, Gorilla.

[Jim Matthews]

Isn't contact cement what is used for counter tops?

[Keith Hankins]

I'd go contact cement and j roller.

[Chris Padilla]

I glued in some plywood with GG this morning. GG can basically glue anything to anything and I have a small bottle that I will go ahead and use up and then I'll try the PVA.

I don't quite see how contact cement would work very well because I have to slide the plywood between the two pieces of masonite and quite frankly, I don't trust it to last.

[Edward Oleen]

According to Matthias Wandel.... of WoodGears.Ca, Gorilla Glue is lousy at crack filling. He tested it, and you can find the video on his site or YouTube.

According to OldEd (lil' ole' ME) Titebond works just great on Masonite, or any other "hard board" ("Masonite" is a brand name...)

I've used it countless times, but only for indoor stuff. The reason is not the glue - it's the masonite: the stuff isn't water-proof and doesn't like to get rained on.

[Marty Gulseth]

I've had good luck using "Liquid Nails" for the back of masonite. Not completely sure if it is still available, I haven't looked for a while.

Regards,

Marty

[Howard Acheson]

>>>> I wonder what the door manufacturer used.

Many commercial door manufacturers use a electric heat activated adhesive. The adhesive cures almost instantaneously.

You do need to have a way of applying pressure to the lamination. Seems like an excuse to buy more clamps.

[Frank Pratt]

I have performed surgery on many hollow core doors & PVA is all I've ever used. The masonite or wood will fail before the glue does.

I think it was Fine Woodworking that did an extensive glue test a while back & found that the Gorilla Glue was no good at all at gap filling. Well, it filled the gaps alright, but wherever there is a gap the glue foams up. That foam, while very sticky, has no strength. I've pretty much given up on GG because PVA or epoxy will out perform it & it's so horribly messy to work with.

[Chris Padilla]

The GG appears to be working just fine. I'll slice things flush tonight and post.

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[Chris Padilla]

Nice clean slice with the track saw...ready to rip a long 1/8" strip of poplar to glue to this edge.

The GG appears to be just fine here. I will use TB-III to glue the poplar edge.

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[Chris Padilla]

Okay, used many clamps despite using the Bowclamp ultimate caul. For whatever reason, it just doesn't seem to apply pressure all along it with thin strip glue ups so I end up adding several extra clamps.

We'll see how things look tonight when I pull the clamps. It doesn't have to be super critical snug/tight/zero gap since this will be painted but I always strive to do the best I can as one day, it may be critical to get things tight tight and I may need a different approach.

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