Acoustic Guitar Construction

I used to clamp bridges the traditional way, but for 3 guitars now, I use a vacuum clamp like a lot of others do.
I experience that during the initial clamping quite a lot of air sucks through the wood under the bridge and comes out with some glue.
Questions: Is this usual, have you seen this also and will it affect the amount of glue under the bridge?
Thanks
Herman

Do you have holes through the bridge and top for pins to index the bridge in place? That would let air through if not a tight fit. What kind of wood are the tops? Would that be porous enough to have air come through? I have had squeeze out after the initial clamp time, glue only, no air and didn't loose vacuum.

No carl, I use pinless bridges and the tops are European Spuce and Red Cedar. The only way I see it, that the air comes through the wood.

It is actually possible to suck out the glue under the bridge. I have gotten in the habit of holding down the bridge for a minute or so as the vacuum forms. Most likely you are seeing squeeze out but it did happen to me once where I did not end up with enough glue. The bridge cleanly popped shortly after I strung up the guitar.

Thanks John for the tip. I glued a bridge on a parlor for my grandson. I pushed the bridge down for 2 minutes till the glue grabbed properly. After connecting the vacuum pump only little glue came out (and no air). For the moment it looks promising. Thanks
Herman