there are a few variables with this one,
are the windows internal or external glazed(are the beads on the inside or outside of the window) if outside,is the dg unit stuck to double sided tape on the inside,if yes,this needs to be cut first,when the unit is out the tape residue needs to be cleaned off the frame and new tape of the same thickness has to be fitted.if it's internally beaded the glass will probably be against a rubber gasket on the outside.
when ordering the glass,you will need to know the colour of the glazing bar(gold,silver,bronze)and the thickness of the unit(this needs to be accurate.units vary from 10mm upto 28mm thick.a 28mm unit for instance is made up of 4mm glass,20mm glazing bar,4mm glass.the easiest way to size the the unit is to measure the old one,failing that,measure to the out side edge of the beads and subtract 10mm from the width and height,this will give you enough space around the glass to fit the plastic packers.
to remove the beads you will need a sturdy scraper the shorter the better,the one i use is about 50mm long not including the handle and about 40mm wide being so short makes it very stiff and it's perfect for removing beads.you will also need a mallet or a nylon hammer.when removing beads always start with the longest side and about 25mm from the corner.push the scraper into the gap between the bead and the frame(it should open up slightly)then tap it in and away from the frame angling it slightly towards the glass,once the bead starts to open up move up the window repeating the process.when you get to roughly the middle you should be able to pull the bead out.the rest of the beads should come out easily once the first one is out,just repeat the process.make sure you take the top bead out last.and please don't be tempted to use something like a screwdriver instead of a scraper,you will damage the frame and probably break the bead.
is the window an opener if yes,is it a side or top opener,if side opener you will need to 'toe and heel' the glass to keep the sash square and stop it from dropping,to do this you need to close the sash into the frame preferably with it packed up from the bottom very slightly,just enough to take it's weight then sit the glass on a couple of packers you then need to wedge the glass in opposite corners making sure the bottom corner is on the hinge side(it needs to be wedged tight).this operation acts basically like the brace on a ledge and brace door and will stop the sash pulling down on the hinges,then re-fit the beads.
to do this can be easier said than done,but basically you need to hook the front of the bead into the the groove that you will see on the inside of the frame then tap it into place you may need to start away from the corner slightly and once you have a couple of inches of the bead seated,slide it into the corner, when this is done you should be able to knock the rest of the bead into place(do the top bead first),the last bead can be the hardest. you need to get both corners in and work you're way to the middle.a small window is difficult because the beads are hard to bend,just remember to remove a long bead first and when re-fitting leave a long bead for last(the longer the bead,the easier it is to fit).
