upcoming cracks underneath?

[chris.oak]

painted my tank all black a while ago but now i got some thin but long cracks in the paint and they are growing everyday, any idea why this is happening?

[mcvierh]

Did you strip to bare metal?.....If not, then thats where the crazing is coming from.

[Doc_Shadow]

Yeah, I was gonna say bad prep.

[chris.oak]

it was sanded down to bare metal, water paper 1200c the finest in last sanding and then 2 layers of primer and after 2 layers of black, no clear as i want to paint it wite flamed.

[Doc_Shadow]

Maybe not cleaned enough after sanding? Bad paint or primer? Could have been the conditions when it was being painted. Maybe primer wasnt dry enough? Im not a painter but just thinking of possible problems.

[Pez]

Painted it awhile ago in Norway..... as in winter? Did you paint it in an unheated garage per chance?

[chris.oak]

garage? what is that? i have built and painted my bike underneath a roof all winter...not the best condition but the only way right now

[chris.oak]

can i sand down the cracks and then paint it over once again or do i have to bare bone it again? i have a dry cloth cabin that i can put it into before and after.

[apache driver]

First of all, 1200 grit is nowhere near coarse enough for primer to adhere to.
Second; what type of primer did you use? if you used spray can primer then almost certainly what is happening is the primer is delaminating from the bare metal.
On bare metal, the metal has to be sanded sufficiently for the primer to bond to I usually use 220, or sometimes 400 if no body work is required, also you HAVE to use self etching or epoxy primer on bare metal, as nothing else will adhere sufficiently; I hear a lot of discussion about painting bike tins with spray paint and I hear a lot of people advising folks to sand the tins to bare metal; that is good advice if using the correct materials for the job (spray paint does not fall into that catagory) when using quality stuff, the best bet is to remove all the old paint and prime with epoxy primer (after cleaning the bare metal sufficiently) then follow up (according to the directions) with a good qualiity surfacer/primer, then a coat of sealer/primer, then paint and clear.
If using spray paint you should never NEVER remove the original paint, there is no spray primer available that adhere's to bare metal as well as factory finish does, so, leave the original paint (sanded with 400), prime with surfacer/primer, sand out all the imperfections from the original finish (repeat as required), apply a coat of sealer, then paint and clear.
So; my guess is that the cracks were caused by the primer delaminating from the bare metal; but what do I know?

[apache driver]

can i sand down the cracks and then paint it over once again or do i have to bare bone it again? i have a dry cloth cabin that i can put it into before and after.

No can do, gotta remove it all and do it right, or you'll have the same problem again.

[chris.oak]

sounds like your right :) thanks for the help and conclusion