I wonder if someone have suggestion for end -grain joint. Yellow glue or white glue?
Any brand?
Thank you
Stefano

More information.

Adam, I'm jointing hard maple picture frames. I'm using white glue instead of yellow because the white have some flexibility and seem to me absorb more the movement of the wood during the change of the weather. 10 minute before I joint the frames I apply 50/50 mixed water/glue to the mitered joints to avoid the wood absorbing too much glue, after 10 minutes I apply the glue and I joint the frames. Doing like so I have strong glued joint but some time after few months some of the joints show a little separation and I wonder if there is a better technique or glue
Thank you

Simply use Titebond1 yellow glue. Do not water it down. Put enough glue on so you need to wipe it off after assembly. Depending on the moulding size you can use a biscuit or spline to help keep it together.

Thank you Adam but the wood need to prepare in some way otherwise the pores of the end grain will absorb part of the glue

Stefano is following the instructions for miters from when white glue was the primary wood glue in use. Pre - Titebond, when Elmer's was it. He probably learned it from the same old codgers I learned it from back in the 60's.

It is good practice - I still use it with TBI when gluing miters, but I omit the water.

Spread a thin bit on each half of the miter and let it sit for a few minutes. Then add a bit more to one side or the other and assemble then clamp, wiping off excess with damp rag.

Be sure the clamping does not distort the frame members. Be certain your wood is the proper moisture content. 6-8% for most of the US is where you need to be.

CSI - Wood:
How wide is the cross section of the frame members?
Species?
When you inspect the joints and find separation, is it always on the inside (heel) or the miter or the toe? This can indicate wood movement from drying.
Is there any visible dried glue in the open joints? Inside edges or outside edges, both or neither?
Are the miters themselves perfect? Test frequently and rigorously, by dry clamping 3 corners. The fourth corner should just touch - not open, not hitting hard. If you don't have that right, no amount or type of glue will correct it.

Thank you David for the beautiful technical informations. I use hard maple and the frames are thin, from 1/2 to 3/4'' faces. Usual separations is from inside, but it's noticeable mostly when I paint the frame white and more that obvious separation is a thin line
Stefano

If inside miters are opening, then your wood is too wet, or your miters are inaccurate, or both.

Normal, seasonal wood movement will never be a factor in a 3/4" wide frame. Maple will move about 0.010" with a 12% to 7% change in MC. Use the "Shrinkulator", check your moisture content, and revisit how you miter, and proof the miters rigorously.

Thank you David for your amazing suggestions. I will buy the moisture meter and check the wood. Do you have idea what will be the best moisture level to glue the wood or much depend of the variation of the moisture once the joint are done?
Thank you

It depends upon your location. In the US Midwest, we use 8% as the Equilibrium Moisture content of hardwoods for interior use. Coastal areas are higher, desert lower.

Bruce Hoadley's "Understanding Wood" is the best book for this type of info. Strongly suggested. It will help you understand the basics, so you don't have to worry about the wrong things.

Thank you David I ordered the book. I'm in New York were there are some climate variations . Humid in the summer and dry during this season. I really want to thank you for all those suggestions
Stefano

We've always used white glue on end grain as its often more forgiving when it comes to movement. If theres a mechanical fix you can use harder glues.
We also tap lots of dents into the ends with the corner of your chisel to give the joint some teeth.