Help! External glazing beads won't come out.

[mothecl]

Hi. I'm planning to replace a load of old DG units that have popped.
Although made of UPVC some off the units have external glazing beads.
I've removed the internal gasket on one of the openers, allowing the glass to move back about 3mm, and tried to remove the beads, but once the gap between bead and frame gets to about 3mm they bind up solid.
I can't find any security foam or whatever and the glass moves easily with the gasket out.
I'm loath to start whacking away at the beads because it's so easy to damage them. The gaskets in the beads are very fine and appear to be bonded to the PVC. I can't create any movement in them at all.
I seem to remember that the builders who fitted these windows had a lot of trouble reassembling them 25 years ago. They eventually had to get someone from the supplier to come and show them how to do it.
Any thoughts? I've done lots of DG repairs and installation going back to the aluminium era, but this one has got me stumped.
Any suggestion gratefully received.
Pics attached.

 

[oldbutnotdead]

You might have more luck by attacking the end of one of the vertical beads. You may get a bit of visible damage where you start but it shouldn't affect the sealing properties. Once you've got the first one off the rest will be easier

 

[opps]

I don't have a lot experience of removing uPVC beads but I have done it before.

I used a Japanese Bakuma cats's claw to lever the beads out, but there are dedicated tools. The Bakuma has a very thin head/blade, so much so that it fits in to the groove and then allows you to lever it. The professional tools are listed below.

Window Bead Removal & Deglazing Tools

Tools to aid in the removal of double glazing window

www.thewindowfittersmate.com

When needed, I have put it in to the gap in the middle of the longest length and then worked my way in both directions. Once that pops out, the rest are lemon squeezy. Go for the middle of the longest length, it will flex more and be easier to pop out

 

[mothecl]

Thanks for the suggestions all.

There's something very fishy about these windows. You'd expect the internal seal to be a wedge gasket, but it was a fir-tree pattern with a "mushroom" on the frame side, suggesting that it's not supposed to be pulled out (see pic)

. This makes no sense with external glazing bars that have bonded on seals

There certainly isn't any 'popping' with these glazing bars. I've tried progressively wedging them out, but they always bind up when the gap's around 3mm - even in the centre of the longest run. After that you start denting the plastic. It feels almost as if it's designed for one-shot assembly.

Wonder if I could fabricate a miniature surgical retractor...