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Glue line in mdf lamination....1/12
I'm laminating two sheets of 3/4" mdf for some end panels ( one layer with the second layer 4-5" wide to build up edges ) so that I can do a contemporary style 1 1/2" radius front edge. The finish will be a white M.L.C. stealth, over clawlock II w/ a clear gloss krystal top coat.. My issue is that I have seen the glue line show at various times in other laminations. This time it's critical.... Whether the glue swelled or the what ever it was, however slight, I don't want to see it again,
I use a titebond glue, but can use something else...possibly even a vac bag for a tight line if suggested ! ?
I need to know that the white gloss will not reveal a glue line now or ever ...any suggestions for any aspect would be appreciated....Thanks ...
Unibond 800 or epoxy. Nothing that is waterborne.
I think you are going to see a glue line some time in its life.
I seal my entire edge with a 50/50 mix of glue and water. I use three coats sanding in between coats. I end up with invisible seams.
The only time I had a glue line show up with yellow glue was when I used a 6" wide strip for the build up. Most of the time I use 2" or less and spring clamps every couple of inches. My thought is that the glue line thickness was the primary factor, that I didn't use enough clamps and/or used too much glue on the 6" wide buildup.
Excess glue is not going to squeeze out on a wide strip as easily as it will on a narrow strip. These days I'd use the same finely notched glue spreader I use for veneering. You should be able to get more PSI with clamps than vacuum, but I'm not sure that matters with a thin and even spread of glue (I haven't done any painted buildups in my vacuum press yet).
we use titebond as well. lay a heavy bead down both sides of the finish edge so that when you put the squeeze clamps on, the glue actually squeezes out. scrape with putty knife after 10 mins. sand with 100 when dry. when invisible seam is required, as johnny means suggests, paint with glue/water mix or use an off the shelf wood hardener liquid. it's usually not the seam itself that shows, it's the area around the seam that shows differently than the seam. glue squeeze-out fills any voids in the actual line. glue/water or hardener fills the pores in the mdf edge. priming with kilz and sanding prior to paint will add another layer of protection.