Removing hard 'sealant' (possibly adhesive) from uPVC window frames??

[Careful_Bodger]

I am trying to clean some uPVC window frames, but the internal corners have been finished with something that does not seem to be silicone. It is quite hard but comes away with scratching, which I don't really want to do. Whatever it is, it is thin with no significant depth.

Any thoughts on removing it back to the original surface? I do appreciate this is likely to be a long shot given difficulties is identifying what might have been used. I have included a pic.

[GALLERY=media, 102580]HardSealantOnUPVCsm by Careful_Bodger posted 15 Feb 2019 at 1:15 PM[/GALLERY]

 

[Tigercubrider]

try some wd40 and a plastic/wood scraper

 

[footprints]

Or Big Wipes.

 

[Nige F]

Looks like painters mate type acrylic filler

 

[Netbo]

try some wd40 and a plastic/wood scraper

Excellent. I was sceptical but worked well using old lolly stick as scraper. I had tried other things which hadn't worked.