On Tue, 28 Apr 2020 17:58:55 -0400, Jack wrote:

On 4/28/2020 1:21 PM, Clare Snyder wrote:
On Tue, 28 Apr 2020 10:52:03 -0400, Jack wrote:

On 4/28/2020 9:29 AM, Mark H wrote:
The plywood is coming apart. The glue is good

This was accounted for in the video, and all glues didn't past muster.
She also tested solid wood. I was surprised by the mitered joints and
how they held up, particularly with epoxy.

Also surprised by how pre-gluing or sizing the edge grain miter joints
didn't help at all. I had read sizing mitered picture frames would
greatly strengthen the joints, and was planning on doing that the next
time I make picture frames even though I have a 100% success rate w/o
doing that. Typically, I just glue them and clamp them with my pin nailer.

The diluted glue used for "priming" the joint left a low strength
"boundary" layer separating the full strength glue from the wood
fibers. PERHAPS letting the prime coat cure before applying the full
strength glue and assembling the joint MAY have improved the results

I think you may be right on that.
Back in the hot hide glue days priming was VERY common. You filled the
end grain, in particular, with glue and let it set - on both surfaces
- then added a "filling" to the sandwich and assembled the joint.