when I slash the top of my loaves why do they seem to join up again ?
The most likely reason seems to me that you are not slashing deep enough. Most recipes specify 1/4-1/2 inch deep cuts. For batards, hold your knife or lame at an angle to the bread - not vertical to it. For boules, I've seen that you should hold the knife vertical to the surface of the loaf.I suppose you could also have this problem if the gluten weren't developed enough, so the dough hadn't sufficient elasticity to spring back when slashed.Just my guesses.!David
In addition to David's guesses, maybe you aren't getting enough oven spring to open the slash.
Are you steaming your oven? This is important to getting good oven spring/opening of the cuts. Also, make sure the loaf is not overproofed.
A technique I have observed is using vegetable oil in the slashed loaves. This is employed by the use of a small squirt bottle, the cut will stay open with the addition of a few drops of oil. I find this technique to be unnecessary if the loaf has enough of a dried outer skin just prior to baking to tolerate a robust, deep (enough) slash. However there may be times when the loaf is extremely wet from conditions that exist in the proofer, the bread needs to be slashed immediatley for an imminent bake. That's the time for the use of oil. Does this help?
Thanks for the tips folks, I think one of the problems is using something sharp enough. I tried using a blade ( a razor blade with a metal saftey edge) but this doesnt seem sharp enough, so I think i'll need to get hold of a lame to hold a proper razor blade.
By the way I tried sourdough ladys loaf and it came out exelent, I also did the pumkin bread that also came out very good to.
Two wrongs don't make a right. Three lefts make a right
From my experience and from what I've read, mainly on this site, a good part of what gives your loaf shape - and causes the slashes to part is surface tension. When shaping your loaf by rolling or folding make sure to stretch the dough some (to the extent that the type of dough/bread/recipe allows). That way your dough has some spring to it. When you slash it the tension will pull the two sides of the slash away from each other.
I've found that speed is important and have seen professional bakers apply it. Slash quickly - don't drag the the razor/knife across the loaf cutting slowly as you go. Plan the slash before you go ahead and make it - depth and direction, because when slashing fast you can't plan as you go along. You should also wet the blade before slashing.