Dirty roof...

[Minnsy]

Acquired car, that has not been looked after too well. After cleaning roof, there is still considerable 'debris' left . Is the answer to wash again, but scrub harder, or will one of these 'clay bars' do the trick. I guess it is a mixture of tree sap, dirt and the general grime...

Thanks

[Nightmare]

has to be clay (or thinners!). if it's sappy or tarry then just scrubbing hard wont ever work (or will take an eternity and make your arm fall off and/or add light scratch damage)......

my personal choice for ease and pleasure of use:
http://www.monzacarcare.com/products/?category_id=...

[belleair302]

Bilt Hamber auto clay is the product to begin with. If that does not remove most of the sap, ingrained dirt then maybe you will have to get a somewhat more aggressive clay and a lubricant.....not Meguiars.

[944Tman]

If you go the BH route, make sure you use loads of water, even running water from a hose, as you can marr the surface of paint if you're not using a proprietary lubricant - water is not slippy so doesn't allow the clay to glide too well, especially in hard water areas.
Meguairs do a Professional Clay Bar, which is about £25 and much firmer than their usual rather crumbly grey clay.