Subject : Using Blocker Posted : 2018-08-13 6:09 PM Post #37811
A couple more test pressings, then to a large round marquetry panel about 35" diameter with several hundred packet scroll sawn pieces, mainly flowers and some leaves.
Quite a few veneer pieces have internal saw cuts where I'm hoping the dark Unibond will come through during vacuum pressing. I've done this many times, but never with Blocker mixed in the adhesive.
With Blocker, is it important to use a plastic putty knife to push the adhesive into the glue side of the assembled marquetry, or will the adhesive come through the same as if Blocker was not in the adhesive?
The concern is that the pieces of veneer will have more time to absorb some moisture from the adhesive, expand against neighboring pieces causing seams to bulge, or larger pieces start to curl and/or wrinkle.
Would it be advisable to store the unmixed adhesive in a fridge overnight to lower its temperature, perhaps slowing movement of moisture into the pieces of marquetry?
Subject : RE: Using Blocker Posted : 2018-08-15 1:13 PM Post #37813 - In reply to #37811
I don't understand why you would use blocker if you want the Unibond to ooze through. I think the longer cure time you'll get by cooling the unibond will override any decrease in moisture absorbtion that MIGHT be achieved. How will you keep the taped up veneer from curling/warping if you apply the glue (with or without blocker) directly to it?Tests are your friends here. Jeff
Subject : RE: Using Blocker Posted : 2018-08-15 7:38 PM Post #37815 - In reply to #37813
Bleeding through some veneers has been known to cause a slight stain of the wood. Once I had the quarter sliced walnut veneer on a king size headboard tinted yellow. My understanding is that Blocker is designed to prevent penetrating through the veneer (bleed through). I don't expect that any such staining along the edges of veneer would be noticeable.
This panel is about 30" in diameter so troweling a thin layer over the entire glue side would take a couple minutes. Yes, I am concerned about the veneer pieces beginning to expand before full pressure in the vacuum bag, but if dark adhesive doesn't come through scroll saw cuts for leaf veins and the edges of flower petals they won'd be noticeable.
Perhaps a medium rolled layer of adhesive on the backer veneer would be adequate?