Advice Needed: Making Double-thickness Mountboard

[Moglet]

Hi all,

I've got an order to get out for tomorrow, and my delivery didn't arrive today. I urgently need to cut a 3000 micron mount in order to finish the project. Can anyone advise me on the best method to bond 2 sheets of board together???

Heeeelllllllppppp!!!!!!!!!!!!!!!!!

[Roboframer]

I've used this stuff applied with a roller and then put in my press.

But I guess diluted builders' PVA would do too.

[prospero]

I think Robo is on the right track there. You really need a wet adhesive under pressure. Prob is with drimouting the two sheets using dm tissue is that the edge of the tissue tends to show along the bevel. You may get the same thing with PVA.
I suppose starch paste is the ideal as it is not shiney. Depends what you have available on the plot.

[Moglet]

Hi guys and thanks for coming back so quick. Prospero, I thought DM tissue would leave a line visible in the bevel alright.

I've got normal schoolkids PVA or PVA-based woodglue as options. Which do ye think would be better, and how dilute does it need to be?

Also, could ye give me a steer on dwell time in the press/temperature settings? Ta!

[Roboframer]

Bond them back to back too, no worries about a different colour or textured surface paper half way through the bevel then.

[Moglet]

Thanks for that, John. Would never have occurred to me.

[Roboframer]

I'd go for the PVA - wood glue dries rock hard, you don't need heat; maybe it would speed the drying up though?

I use a hard bed press and don't turn it on! You could just plonk a lite of glass and a few heavy things on top.

Dilution's not critical - I'd probably not dilute the kids type PVA - I don't dilute the lineco one,

Never thought of using starch paste for this - big props Prosp

[prospero]

I just cut a bevel on two scrap bits. Then when I noticed the line down the middle I tried two more back to back. It didn't occur to me either.

Anyhow, the result is not too bad. You can see the join, but a blind man would be glad to. I very light stroking with fine sanding block improves it slightly.

[Bill Henry]

Difficult problem, that. I’m not speaking from experience, just musing.

I’ve never tried bonding two sheets of mat board using PVA. My concern would be that the moisture in the adhesive might cause the mats to warp. That, plus, if you’re in a hurry, it might take too much time to dry.

Since Fusion 4000 doesn’t have a paper substrate, it might work without leaving a seam. Likewise, perhaps PMA might work, too.

(Three minutes, forty-seven seconds pass … )

I just tried placing two sheets of Alphamat (a pale blue) back-to-back with PMA. There was a very slight, but still noticeable seam. I don’t think it was from the adhesive, though; I’m guessing it was simply the interface between the two boards.

But placing the mats back-to-back resulted in the surface paper of the bottom mat showing ever so slightly. You could always do them back-to-back and tell your customer that it was a clever design feature. Even if you used a solid “Museum” mats, I think you’d still have that faint seam.

Trying to strip the surface paper from the core of Alphamat or Rag Mat would leave too much of a raggedy edge, I believe.

I’m not sure there is any perfect solution to your problem.

[Spit]

Is it possible to peel off the facing/backing paper?

*dang, Bill beat me to it*

[Roboframer]

(Best nerd impression please......) I think you'll find that If you peel off the facing paper it won't be 3000 microns.

(Nerd impression off) If it's a neutral colour it's not much of an issue - also check out your normal 4 ply bevels sometime - depending on who you use, you can sometimes count the 'plys' anyway!

Confession - I do this bonding all the time - well, when I need to - my normal step up from 4 ply is a bevelled accent, I never buy UT mountboard, it's a great way of using scuffed offcuts, slow moving colours or the bigger fallouts from double mounts that have ATG on them etc etc.

[prospero]

Don't think there is a solution to the join line. It's not really that unsightly...... Some of the thicker rag boards I have used have a prominent join line on the bevel.
Don't think the adhesive is really the prob, it's really only a double mount by any other name.

[JFeig]

I have made super heavy boards made up to 4 layers thick!

I have always used starch paste. If you did not have any in stock you can go to the paint store and purchase some old fashion premixed wallpaper paste. The newer formulas have some PVA. These pastes have stabilizers and preservation chemicals, so they are not considered pure conservation products, but they work fine.

I place the sandwich of boards and paste in my vacuum press for several minutes, then let the boards dry under a sheet or two of plate glass (6mm). The plate glass was recovered from several broken shop windows. I have seamed the edges with a stone and then taped with self adhesive kraft tape.

[Moglet]

Thanks so much guys for all the great tips and advice, and for such ultra-fast responses!

I have a vacuum press, so I'm half-way there with the bonding. The job is for pick-up on Friday morning, so if I leave the assembly till tomorrow night, there should be a fair bit of drying time under the weights. I'll let you know how it goes.

Thanks again for all your help; it's so very much appreciated!

[Roboframer]

I like my hard bed press - but bonding? That's just weird!

[Roboframer]

Sidenote (IOW 'Frankenthread') Anyone want any 6mm (at least) safety/toughened type glass?

I've a shedload under my porch - er so that's a porchload .... still there from the last place, who used a lot of glass display units - all the edges are rounded - it's mainly long and thin but there are some nice squares/rectangles.

I think it's safety/toughened - I'll take a hammer to a piece tomorrow and report back!

[The Crofter]

My first thought would be to turn the join into a "feature" and not try to disguise it. Perhaps using a third board with a different coloured core and creating a sandwich. The join between each board would be visible but not obvious. A black core board in the middle could look stunning and certainly different. Can't speak from experience and this might be total carp but who knows

[Spit]

You've just reminded me that I still have some 8mm bulletproof laminate glass from the old Post Orifice in the garage - useful if I need some flat weight.

[Roboframer]

Perhaps using a third board ........ A black core board in the middle could look stunning

Great for framing some liquorice allsorts! But how you gonna cut that 4.5mm thing, Bertie? (*)

Part of the reason I don't plug UT mountboard is that it's a pain to cut - can't be fussed with resetting blade depth and recalibrating stops - can't just do that and off to go anyway - you have to practice on offcuts to eliminate over/undercuts - and that blunts the blade ..... new blade performs different blah blah. Too much grief - have 1.5mm, or that plus a bevelled accent - not much price diffo - convenience vv time.

(*)CMC?

[Not your average framer]

During my time as a bookbinder, (now a few years back), you could always spot where two thicknesses of boards had been glued together. The trouble is the lack of uniformity, there's something else in the middle, which is the glue.

I sometines glue layers of scrap mountboard together for making deep bevel mounts, which are either wrapped with a deep bevel tape or sealed and painted. Unfortunately it is my experience, that until you cover the bevel, there is always a glue line.

As I only ever do it with PVA, I cannot offer any meaning full comments as to if one type of glue is better than another.