OT: Paint reaction.

What is the halfords primer filler? is it filler or primer? or is it like a thick primer?

Is it the existing paint that is not happy with the primer filler stuff?, or the new coat you are trying to put on top of the primer filler?

I found that you got wierd effects like you are describing when i tried to spray some halfords spray paint (which was acryillic paint) on top of a piece of car that was painted with cellulose.

They obviously dont like to mix!

Is the halfords primer filler stuff a acrylic paint, and you are trying to put it on top of a different type of paint?

The probable cause is solvent reaction.

Paint manufacturers are not always compatible with others even when using the same paint type, Cellulose for example or cellulose thinners is not always compatible with itself, meaning you can paint a vehicle in a particular batch of cellulose paint and a week later re-paint the same panel and you can encounter paint reactions simply because the thinner is reacting with itself by re-softening the underneath layers, which is exactly how cellulose finishing is supposed to work.

Primer surfacers can also cause reactions because primer is applied thicker and the solvent has a chance to penetrate or react with inner layers leading to pickling.

The possible cure:

You could seal or isolate the affected area by using something like Barcote or better still apply heat to warm the panel first and then build up layer upon layer of primer each as a dry coat, this will stop further reactions appearing with the primer given less time to react.

Primer does not act as a sealer it simply builds up layers to create a level area which should avoid the hollow which often shows up on repair work. Primer will hide a multitude of sins but it will not seal them.

It is possible to paint over acrylic with cellulose but not recommended the other way round. Also aerosols use much thinner paint material to force it out of the can and this is notorious for causing pickling when doing repair work.

Recently applied paint or softer paintwork is more likely to sustain reactions than older hardened paint.

Steve.

Thanks Steve, I've just got some sealer I'll let you know how I go on. As always I've learned something new again from you and you put it across well (I understood it without having to read it twice - now for the instructions for my new spray gun....).

Regards

Lee D

[snip]

No problem Lee, Sometimes I have to read things I've just written twice (I must have been on a roll last night), Just hope I'm right with my diagnosis with not seeing the paintwork, But I couldn't just sit back and see you struggle.

The sealer will definitely do the trick though, do let me know how you get on ;)

Steve.

:0)

The sealer did the trick. got the sealer on all the way around, flatted and two coats of primer on too. Not bad given I had to scrounge the Disco off Mrs D as the 101 is misisng... walked home after dropping the Disco off. Got all set up and ready to go with my first mix of sealer in the new HVLP gun. pulled the trigger and the blasted thing snapped the pin which is part of the trigger....grrrrr!!

Anyway I risked the 101 and managed to get a replacement. 101 was running ok too which is most strange.

I also managed to eventually discover that the pressure guage on the compressor doesn't really do justice for the pressure at the other end of the hose, but then I'm running a 20 metre extension hose.

I'm going to flat off the primer shortly and fingers crossed for a dry morning. I'm working in a £30 3m by 6m garden pavillion.

Thus far I'm impressed with the low amoounts of overspray. I expected much more but I guess the HVLP gun helps alot with that.

I think the sealer also did me a favour as by the time I'd put the sealer on then worked out after the first layer of primer that the pressure wasn't enough the second layer went on much more easily.

I'll be well chuffed it the top coat goes on as well. If it does rain in the morning am I best avoiding the top coat yet? I've got anti bloom thinners and also the laqure is wixed in with the top coat.

As always I've rattled a few piccys off which I'll upload soon.

Lee D

The sealer route is a guaranteed solvent reation free method.

A 20 meter hose at 1/4 bore will lose about 60psi by the time it gets to the gun. The compresser will need to churn out about 120psi to cope, however in your case using a HVLP gun which is designed to use as little as 10-20psi for most jobs would counteract this pressure drop.

Plenty of ventilation for you then, watch the flies though ;(

How did you find the HVLP gun?, It took me a while to get used to one after sprying at 50-60psi most of the time in cellulose finishes. IIRC the overspray or paint waste is reduced by 75% making spraying more economical and cost effective.

Usually you would leave primer overnight to harden sufficiently ready for a wet flat next morning but don't forget to use soap or pour some fairy liquid in your bucket to stop the wet-or-dry from clogging up.

Unless you're unlucky and get a considerable damp or cold spell you won't need anti-bloom thinners but if you do use it remember it takes longer to dry than standard or top gloss thinners if you want to avoid runs etc.

I have a look later ;)

Steve.

When i did my car last year i didnt leave it overnight for the primer coat to dry. I put 2 coats of primer on in fairly quick succession and then left it for an hour or so while i had my lunch before starting my top coats!

What else would i have achieved if i had left the primer to dry for longer? The finish i got doesnt seem overly bad - the only problems i can see i have put down to insufficient surface prep, and where it has shrunk very slightly over the filler.

I didnt have any trouble from the cold when i did my car at the end of last year. I was in a garage (which was unheated apart from my leccy heater). There was frost on the roof when i was out there and i didnt get warm enough to take my coat off all day - So you should be okay in the temperatures we are getting now! I used normal thinners and lots of very thin coats. I got a better finish on those bits than i did on the stuff i did in the warm a month or two earlier!

Are you gonna do morph after alfie? - else the 101's are going to be twins again as i have some nice shiny bare ally now!

I'm just concerned about moisture in the air if it's raining. The Pavillion is thus far watertight just wondered if rain would affect play or if it's more mist and see your breath type weather that's the problem.

I'll be starting with 50/50 unless anyone cares to suggest more thinners? hic.. #..?.! ;0)

Yup, but I do have lots more prep to do on Morph, though I think I will br spraying him given the finish on the primer then I'd be happy with that on Morph as I don't think there is a gloss on the paint I got, least I've not see any sparkle in the desert militray arena but for Toyotas with Gattling guns in the back. Infact primer grey is growing on me, shame to spoil it really. Only down side to spraying Morph is having nothing big enough to put him under.

You still going with the Roses chocolates theme ;0)

Lee D

Ive just remembered when i did my front spoiler. It started pissing it down and thundering about 2 minutes after i started spraying the top coat and didnt stop. That bloomed quite a bit and even now hasnt polished up as well as other bits.

While i was doing the rest, it was see-your-breath weather and it was fine with good thin paint. I also got the odd shower while doing some of it - but as long as it didnt get humid too it was fine. I think that biref showers are fine - its just heavy rain or when it gets too humid that causes hassle.

Thats what i started with when i did the first bit of my car. I was on more like 40/60 paint/thinners, or even thinner (like 30/70) by the time i had worked round the the last bits of car and got the hang of it better.

The last bits were much easier and im much happier with the finish.

Lots of thin coats works a lot better than fewer thick ones and gives more gloss it is also a lot easier to keep the 'wet-edge' going when the paint is thinner and takes longer to dry. If you leave the paint too thick then it dries so quickly that you cant see where you have been!

Remember that when the paint is thinner to not spray it too deep as then it will run - which is whiy i'd go for lots of quick thin coats..

it needs a sunny weekend! Hard thing to guarantee round here!

Nobody i have mentioned it to is convinced, yet it works in my mind! I need to work out photoshop and sort out a mock up first really!

If you are just providing a layer of protection then you can spray right on top but not if you have hollow repair areas to build up. Primer is supposed to be wet flatted or at least rubbed over to provide a key but it's particularly important to leave overnight after repair work when the primer must be left to dry thoroughly otherwise you'll always get those sinkages called "fried eggs" especially in cellulose.

None except in Lee's case the wing area had been repaired in which case the primer will need building up to beyond the existing layer and then (next day) flatted to the same level to achieve the best repair.

This would be eliminated if you left the primer to dry thoroughly overnight and then flatted out the sinkage before applying your top coats.

That would also depend on the type of thinners used, some thinners are more susceptible to blooming than others.

Steve.

Thanks! I had just thought that the 'sinking;' was due to my not getting the filled sections quite level when i'd rubbed them down or something. Next time i will try and leave it overnight to dry. This makes sense now. Kinda hard to get 2 consequtive dry days of work sometimes though :( - Which is why i tried to do it all in one day before. I did wet flat the primer layers before going over them again.

I did read your website before trying anything!.. When are you going to add a spraying section that covers this? :)

I was using standard £3.95/gallon cellulose thinners.

First time I've used any gun to put paint on so I couldn't really tell.

Flatted last night but left overnight for the top coat.

H'mm I used the Anti bloom as thats all I had, bit belt and braces but rather that way than the other.

Right... now I've demasked how long before I can rinse off the dust?

The finish is...er.... Blue! :0) .. and all the panels are the same colour. A good polish and Alfie will be his old self again.

And at last I don't have to go to work early in the dark ;0). Just hope this layer gets over the cloaking device which seems to self activate. (I.e. others can now see Alfie "the incredible invisible Range Rover" rather than run into me)

Lee D

Probably better for you then to use the HVLP from scratch.

Good idea, this allows the paint to breath after flatting which softens it and harden off again.

A couple of days is usually sufficient.

Indeed!

Steve.

[snip]

I'm working on a project that should fill the gap with reference to spraying, Spraying is just one particular subject I intend to include in an illustrated book showing the stages from start to finish in both synthetic coachpainting and Cellulose spraying. I already have a publisher waiting in the wings, I just hope it generates sufficient interest ;-)

Standard thinners can fair quite well it's the higher quality or top gloss thinners that are more prone to bloomimg.

Steve.

Having got over the shock of having a car all one colour I came back down to earth this morning. There was a nasty coarseness to some areas of the paint and reflections aren't really existant on the inital finish,

Ok ok I admit it, I flatted , t-cut and polished a small area (which will be hidden by a bumper end cap).

WOW!

If the rest of the car turns out so well I'm going to be one Happy Chicken. I could see reflections in it! NO I MEAN LIKE SHINNEY ONES!!!

My main question now is how long before I can safely flat, t-cut and polish the rest... and where does compound fit in to it? Is it like T cut?

I'm thinking along the lines of soapy 1000 then soapy 1200 grit , T-cut then Mer polish (what I happened to have at hand anyway).

Also buffers.... what stage should / would you use one? I've a urge for such tools and a large compressor which should power one.

Count me in for a book purchase, I've tried two techniques now, synthetic with a roller and now cellulose with a gun and I could send you some piccys from a first timers crack based on your pointers... The roller one is here...

Alfies piccys will be along post polishing.

Lee D

Thats what i did to the first bit of my car. By the time i got to the last bits i didnt need to t-cut it afterwards to get the shine! :)

So by the time youve done the 2 back corners you should be good at it!.

I did it all in the same day...... and didn't get any better at it. BUT I'm not too disappointed as I now know what it will polish up like.

Lee D

Cellulose can provide outstanding mirror finish results if you put the time in on the prep and work the paint properly.

You can quite safely flat now, normally though cellulose required a week or more to cure thoroughly which is when you're supposed to polish it but no one waits a week, waiting a week allows the paint to settle or sink if you polish it straight away there is a possibility of certain repair areas sinking again but that's not usually a problem on a Landy.

1000 is an ideal grade, 1200 might be a bit too fine but I wouldn't use T-cut it's also too fine, T-cut is more a cleanser that a true polish a bit like Brasso, What you should use is proper rubbing compound like Farecla G3 which is suitable for hand or machine polishing/compounding.

You can use a buffer now but still use Farecla G3 as the polishing medium.

I'll announce the book here when it's done, probably next year as it's going to be quite comprehensive.

Did you say what colour you've used?

Steve.

Will look forward to that.

Percy the IIa was rollered in a VW Green colour. I was looking for something similar to the Heritage green of Landrover.

Alfie the Range Rover is in Plymouth Blue.

Lee D