Interior Mirror Adhesive Pad

Has anyone successfully managed to reapply a rear view mirror,  that has come away from the windscreen?

I  have tried 2 'Pearl' Mirror adhesive pads.
They claimed to be heavy duty but despite me thoroughly cleaning both surfaces,  they couldn't hold the weight of the mirror, for very long. 

I even tried by sticking the pad to the metal plate, leaving it 24hours,  then sticking the metal plate to the  screen and leaving it 24hours   then attaching the mirror to the plate,. (It would hold for a few hour's, then fall away, leaving the pad stuck to the screen. 

Does anyone know of a product that can cope with the weight of our mirrors?

Thank you. 

I had the same problem with a car (forget which). Windscreen replacement bloke did it. "Special glue". Never found out what. Could you give that a try? 

Hi did you use methylated spirit to clean the glass? If not get some and clean the glass with it.

I had a go at detaching one from a (non MG) car I was scrapping recently and this really was stuck so hard that eventually after trying in vain to get a variety of scrapers and tools between the mounting pad and screen the metal pad broke in half and the screen shattered withe the remaining bits still stuck to the broken glass.
This was fine as I had not counted on being able to save either the mirror mount or the screen so this was idle curiosity at it's destructive best, As far as I could see it had been glued in place by something that looked very much like black windscreen sealant.

This stuff impressed me so much that when I needed to buy some sealant to reseal around the outside facing edges of a glass panel in a sliding patio door I bought windscreen sealant on a whim rather than the usual silicone stuff.  Though its properties could be described in similar terms, remaining flexible etc, it really is in quite a different league for adhesion and IMHO definitely worth the extra cost. 

Somebody at work accidentally stuck some 3m pad material to a desk, we couldn't get it off for love nor money.
https://www.3m.co.uk/3M/en_GB/bonding-and-assembly-uk/double-sided-tape/

I used white vinegar, maybe its not as effective. 

Thanks, if I get no success with another brand of pads, I will go down the route of permanent fix adhesive.

Acetic acid (Wite vinegar) will be useless) as suggested use any decent solvent to remove grease etc, methylated spirits, Iso propanol Alcohol or even automotive paint thinners. Make sure you have a decent brand of adhesive pads that are not old stock. I had a similar problem nearly forty years ago and a different brand worked first time and lasted for years.

I’ve always been impressed with, use & would recommend 3M double sided tapes. When cleaning surfaces, such glass, you need to get those surfaces chemically clean. Isopropyl alcohol is suitable but to cut right back, acetone is the easiest to obtain.
The days of being able to easily buy from an industrial chemist, “super solvents” such as trichloroethane or carbon tetrochloride, both of which would take the shell of a tortoise, are long gone
M

Many years ago when the rear view mirror feel of in my F, I took the car to a automotive glass installer and they reglued the mirror mount to the glass free of charge.

Update: Problem Solved 

For anyone else with this problem I originally posted about,  the solution I tried and was successful with,  was using 'Locktight 'Rear View Mirror Adhesive 319'.

It comes as a glue, with a gauze which you cut to size.
I slid  the metal back plate out of the mirror,  cleaned both windscreen  and metal plate using acetone nail varnish remover,  washed it again with water.
Once it dried,  I cut the gauze to the shape of the metal plate,  applied Adhesive, placed the gauze on top of the Adhesive,  lined the plate up  paralell to the shaded area on the windscreen,  pressed the loaded plate to the screen for a minute, then left the bond to cure for 2 days,  before reattaching the mirror to the plate. 

Its held firm for a week now, despite some really hot weather. 

Thanks to everyone who contributed to the solution. 

Well done and thanks. I have previously failed in that endeavour.