Primer filler defect

[truckdoctor]

Iv'e had a disaster today in the garage, after thining Cellulose primer filler 50% with good thinners, wiping down the panel etc this happend

It looks like the paint has shrunk and cracked. Is that possible,Whats going on????????
Help please, what am I doing wrong.

 

[steveo3002]

thinners has bitten into whats underneath ...

either sand it all off and start with bare metal or sand up whats there and go for light coats , 50% sounds like alot of thinners to me

 

[truckdoctor]

thinners has bitten into whats underneath ...

either sand it all off and start with bare metal or sand up whats there and go for light coats , 50% sounds like alot of thinners to me

The paint did seem very thin and see through, it did take several applictions to cover. What's the best ratio of primer to thinners please?

 

[steveo3002]

i dont use celly myself ...if i had to guess id go for about 20% and see if it sprays

but ask where you got it from they should have a tech sheet for it

could be a chips away type paint job you went over , that always used to do that when i had to put thier shoddy work right lol

 

[norsa]

not to denigrate Steveos explaination at all but i would say its a non compatible substrate. Suggest the paint is synthetic?
Nick

 

[piman]

Hello TD,

50% thinners is correct for cellulose, if you have some spare sheet steel, prep that and give it a coat or two. That way you will know if it's your paint or what you are painting over.

Alec

 

[steveo3002]

im not saying the paint is faulty...its the heavy thinners content upsetting whats under it , i doubt original factory paint would react like that , but yeah synthetic or some kind of cheapo job would

 

[norsa]

we wait with baited breath

 

[truckdoctor]

I did notice the original paint was very soft under the first coat that cracked, so I guess it must be reacting with the cellulose. I have no idea what the existing paint is ( 2 pack etc.) but I'm stuck using cellulose as it's a DIY job at home, so not even sure if you can paint over 2 pack with cellulose?
I filled the cracked primer filler with body filler and rubbed off smooth. Next a new coat of primer filler with less thinner(20% as instructed) and also warmed the panel, this time success, it covered OK.

 

[norsa]

Celly will go over 2k no problem as its considered original finish. Did your flatting paper clog up easily when you keyed the original paint, pre primer?

 

[Lawnmowerboy]

Filler primer is meant to go on thicker to hide the defect and fill all the little pits. It's no better than standard primer if you thin it down that much. I would use 30% thinners max.

 

[langy]

not to denigrate Steveos explaination at all but i would say its a non compatible substrate. Suggest the paint is synthetic?
Nick

x 2 Nick

 

[truckdoctor]

Celly will go over 2k no problem as its considered original finish. Did your flatting paper clog up easily when you keyed the original paint, pre primer?

Yes it did, it did seem soft, the roof paint had shrunk and cracked open and I filled and painted over with no problems. That was a year ago and so far not to bad.
So I gues this problem is all down to the underlying paint and cellolose reaction. Going to try some gloss and 50% thinner and see what happens, and warm things up first.
Thanks for all your replies, very helpfull.
Steve

 

[norsa]

Still have a feeling its been refinished in synthetic at some stage which is why you are getting this cracking and in time, anything you get on top will crack as the non drying synthetic moves. I would hate to see you waste paint so do us both a favour. What vehicle is it? Can you make an indent in the top coat or even scratch it off with a firm thumbnail? Really wish I could see the car, I would be able to tell immediately.

 

[the snooper]

synthetic lovely stuff, sticks to any and everything and sticks your nose up like nothing else if you get a whiff of it

 

[vdubz]

What vehicle is it?

Looks like a rover p5 i think

 

[anjum]

Might be worth trying some epoxy primer first over the original paint. Key it well first.

 

[steveo3002]

if youve filled cracks in the paint it wont last , chances are once the sun gets on it the problem paint underneath will warm up and move around making more cracks or sinkage patterns

 

[langy]

if youve filled cracks in the paint it wont last , chances are once the sun gets on it the problem paint underneath will warm up and move around making more cracks or sinkage patterns

X 2, needs to go back to metal really, it's never gonna last otherwise

 

[truckdoctor]

Here is a picture, Yes rover p5b

I painted the front wing ( in primer )and warmed it up first with a fan heater, it went on lovely and has no fault, then painted the door jam without warming it up and bingo, same paint defect. Definately temperature related. If I'm painting over synthetic ? it seems ok if it's warm.
Do you think i'll get away with it?