dried lake bed finish on cellulose.

[Johno]

I sprayed the engine bay, windscreen frame and door.reveals of my mk I'd spirits last oct9th it was still 16 degrees and dry. Paints looked good all winter although I've just seen micro crazing like a lake bed a couple of weeks after that warm weather we've had. The car is still in the garage and basically a shell. Any ideas why it's crazed?

Oh zinc 182 primer, cellulose primer filler, cellulose top coat.

 

Regards John'o

[NonMember]

As Mathew says, it's shrinkage. Commonly caused by not letting the primer layers cure enough before over-coating, or by putting the filler primer on too thick. It can also be caused by contamination, although that normally causes blistering or flaking, or incompatible paint types (which you shouldn't have suffered with that list).

[chrishawley]

Does it look rather like the attached photograph?

Worth getting many opinions of this: But just to get the ball rolling with a couple of ideas:

• Keying: One cause is lack of keying between one or more coats. Even if it's primer over the same primer it still requires keying. Conversely, keying with too fine a grade of wet'n'dry gives such a smooth surface that it's akin to not keying at all. At risk of making a huge generalisation a 400 grade WND is commonly used.

• Cellulose behaves very differently to 2-pack. 2K hardens by chemical reaction so a 2K primer, even under faily cool ambient conditions, will be near fully hardened within a day or two. Cellulose drys by evaporation and although it may 'skin over' fairly quickly full thickness drying can takes days or even weeks (depending on ambient conditions). If then overcoated the settling and shrinkage the will proceed even slower rate.

• I like 182 for certain situations but I have had adverse occurences with it. Having applied a thick coat (which I though was dry) it got 'woken up' by the thinners in subsequent coats and crazed severely over a couple of weeks.

Might you consider moving over to 2K?

 

 

[Johno]

So I'm a bluff traditionalist and quite like cellulose for its flexibility and ability to be restored. I take your points though.

Ref the to.e line it's only just now that I've realised the craking. It kind of looks like that crazed pattern but no breaks in the skin although a finger nail could feel it.

 

For. What unread g and hearing I think no gap, day wise between primer and top coat may. Be the amswer.

 

In an ideal world anyone in bristolians a paint booth😁😁

[dannyb]

I had exactly the same on just the boot lid when using cellulose. It was due to silicone contamination, probably from polish. Although rubbed Ed down and ubdercoted it came through overnight. It was back to bare metal and another respray. 

Danny