Protecting cellulose

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Mark Wilson
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Protecting cellulose

Postby Mark Wilson » Thu Jan 24, 2019 10:41 am

I've finally got all panels (apart from the rear roof) fettled and tweaked into position - days and days of bolting and unbolting wings, doors, bonnet and front panel. I'd sprayed everything in advance, well over a year ago, so the paint has had plenty of time to cure. But I think I'm going to have to recoat the whole lot, as every time I move anything I damage the paint. The primer hasn't been damaged, but the slightest touch from another piece of metal and the cellulose scratches off.

I'm not complaining about the extra work, it is probably inevitable when you work single handed in cramped conditions. I am worried, though, about the durability of the cellulose in use. Is there any effective way of protecting it - clear coat, hard glaze waxes etc? With hindsight I wish I'd sent it off for spraying in two pack...

Just as an observation, once I'd got the last wing and front panel where I wanted them, I took them off again to paint the edges of the holes which I'd had to lengthen by filing. I suspect most people on here would have done the same, but would a professional restorer? Hard to see how they could afford to, or how anyone could afford the final cost if they did. :-?

Mark

oliver90owner
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Re: Protecting cellulose

Postby oliver90owner » Thu Jan 24, 2019 10:52 am

Two points.

1). Did you use a hardener in your top coat?

2). Primer is not necessarily waterproof.

StillGotMy1stCar
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Re: Protecting cellulose

Postby StillGotMy1stCar » Thu Jan 24, 2019 11:24 am

oliver90owner wrote:
Thu Jan 24, 2019 10:52 am
Two points.

1). Did you use a hardener in your top coat?

2). Primer is not necessarily waterproof.
Interesting, I have never heard of a hardener for cellulose paint, it dries by evaporation.

ManyMinors
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Re: Protecting cellulose

Postby ManyMinors » Thu Jan 24, 2019 11:30 am

Cellulose paint shouldn't come off so easily if it is a) Good quality. or b) If the preparation was carried out correctly. When I restored my own Traveller I sprayed the body with the front doors and front wings already fitted (as was done at the factory) to eliminated damaging the paint on panel edges which is so easy to do. However, All the rear panels had to be sprayed "off the car" and so was the front panel, grille and bumper valance. I didn't have any problems though and I had trial fitted all these panels prior to painting so didn't need to file out any fixing holes after painting. I don't think there will be any way of added a protective coat to the paint afterwards. If touching-up won't work, I would guess that a respray of the car is the only option. If the cellulose is not adhered properly to the primer though, I'm not sure that simply respraying over it will be an option?

I have never heard of a hardener being used in cellulose paint as Oliver seems to suggest. He is right that primer is not generally waterproof but it doesn't sound as if you have left it in primer in any case.

It sounds as if you might do well to talk to a paint sprayer locally before you finish fitting the car up? Most sprayers will want to carry out their own preparation - especially if you want them to guarantee their work afterwards.

It is a blow isn't it. Good luck in whatever course you decide to take.

Mark Wilson
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Re: Protecting cellulose

Postby Mark Wilson » Thu Jan 24, 2019 2:51 pm

Thanks for advice. It didn't stay in primer for any length of time, and hasn't been out of my dry garage since before prep and primer. The paint was all from Jawel, which I think others have found to be ok, and I've never come across advice to add a hardener.

I might be overstating the problem a bit, in that any damage is the predictable result of impact rather than paint flaking off. I'm more concerned about the ability of the paint to resist everyday stone chips and minor knocks. No enthusiasts for protective glazes out there?

I didn't expect to have to do quite as much to refit panels that were nearly all on the car previously, the problem is that I have become a bit of a perfectionist over panel gaps and alignment and it was a mess when I acquired it. If I did another I would follow ManyMinor's advice and paint with the wings and doors on, but I haven't enough years left in me to do another at my rate of progress!

I intend now to touch in all the damage, flat all the paint down to 1000 grit and add another couple of coats when the weather warms up again.

les
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Re: Protecting cellulose

Postby les » Thu Jan 24, 2019 4:06 pm

Hardener in cellulose? So that’s where I’ve been going wrong! :D


Myrtles Man
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Re: Protecting cellulose

Postby Myrtles Man » Thu Jan 24, 2019 4:16 pm

When cars were still painted in celly by the factories, I assume (always a risky thing to do, I know) that the low-bake oven treatment created a hardened paint finish and, if so, it would probably be as well to only apply cellulose in the same blisteringly hot summer conditions as we enjoyed/suffered (delete as appropriate) last year.

ManyMinors
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Re: Protecting cellulose

Postby ManyMinors » Thu Jan 24, 2019 5:17 pm

The last thing you want want when spraying cellulose is blisteringly hot conditions because the paint will be almost dry before it even reaches the car. Just dry and warm would be perfect. I have never heard of cellulose being baked in an oven myself. The whole point of cellulose in vehicle refinishing was that it is simple to use in an ordinary workshop because it is an air drying product. Cellulose paints have not been used on car production lines for a very very long time.

Mark Wilson
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Re: Protecting cellulose

Postby Mark Wilson » Thu Jan 24, 2019 5:46 pm

I've got my fingers crossed for late April! (or late May if April's not warm.....)

SteveClem
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Re: Protecting cellulose

Postby SteveClem » Thu Jan 24, 2019 6:48 pm

Cellulose is ok and amateur friendly, but nowhere near as tough as modern paints in my experience.

Myrtles Man
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Re: Protecting cellulose

Postby Myrtles Man » Thu Jan 24, 2019 8:25 pm

ManyMinors wrote:
Thu Jan 24, 2019 5:17 pm
The last thing you want want when spraying cellulose is blisteringly hot conditions because the paint will be almost dry before it even reaches the car. Just dry and warm would be perfect. I have never heard of cellulose being baked in an oven myself. The whole point of cellulose in vehicle refinishing was that it is simple to use in an ordinary workshop because it is an air drying product. Cellulose paints have not been used on car production lines for a very very long time.

Well, I'm certainly happy to bow to your superior knowledge in the matter although, from my own experience, I had a Rover P6 resprayed in the early eighties and it was dried in a low bake. I've always been of the understanding that it was painted in cellulose but maybe I've been labouring under a misconception all these years and it was actually done in two-pack. No way of telling now though as both the car and the garage that did the work have disappeared into the mists of time.

PaulTubby
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Re: Protecting cellulose

Postby PaulTubby » Mon Feb 11, 2019 3:24 pm

Cellulose paint is excellent for diy use and easy to use but you do need plenty of coats to get some depth and be able to wet flat and cut back etc. If the primmer was flatted well and keyed then the cellulose should of stuck well. I love two pack but if you get a stone chip with the paint being thicker you get a deep stone chip. Both cellulose and two pack will chip if it gets caught ir knocked. Ideally panels should off been trial fitted. Adjusted. Wing holes elongated etc before painting. You can use masking tape a few layers to protect things from knocks and scratches etc. This does work well I’ve found on assembling.

surfbum
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Re: Protecting cellulose

Postby surfbum » Wed Feb 13, 2019 10:21 am

I think a 1000 wet and dry is too fine to provide a key, did you rub down to that when, you did the gloss coat. I usually go to 400.

Cheers Keith.

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Re: Protecting cellulose

Postby kennatt » Wed Feb 13, 2019 5:34 pm

mark you can put clear coat on top of celly which does give a harder finish (called clear over base) but needs to be done as a final top coat,if you flat the now cured celly which you would need to do ,any slight scratch or flatting mark will show up and be very difficult to get rid of. It's always a problem to as to what to do,if you fettle the panels and then paint, the paint misses under edges and rust sets in unless you have covered the joints in seam sealer,do the panels inside and out and you risk damage on fitting. No easy answer. As far as 2 pack is concerned there is a bit of an urban myth regarding the dangers,allthough it need to be treated with care but the dangers are a bit overrated,as long as you are not actually spraying it as a job and just doing one job ,most auto paint suppliers stock decent filter masks and done outside on the right day isn't such a deathly activity.2 pack primer is excellent in that it doesn't sink into any fillings or react with it so no more of the dredded filler rings. Back in the 90ies I did about three cars in 2 k still breathing normally now .good luck with it

Mark Wilson
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Re: Protecting cellulose

Postby Mark Wilson » Wed Feb 13, 2019 11:04 pm

Kennatt, thanks for the advice, sounds like I'll be best flatting the existing celly, then recoating, reflatting and polishing. I'll have to accept that I'll need to touch in from time to time. Too late to start again in 2K, but I would do it differently if I was starting again.

Keith, from memory I think I went to 800 on the primer. I have been advised previously that I needn't key too aggressively for final coats over the existing top coat as the thinners will melt into the existing celly. Interested if Kennatt has a view on this - when you talk about the now cured celly does this mean that the new coats won't bond without keying?

kennatt
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Re: Protecting cellulose

Postby kennatt » Thu Feb 14, 2019 9:18 am

when I was involved in coachwork (Family garage in another life) we used to use a da (Random orbital) sander with 320 0r finer grit paper dry. But the recommendation for hand flatting was for ....solid colour 500 or finer wet (I use soapy water) Metalic wet 800 or less. Avoid at all cost a circular motion it will leave swirl's which will show through just back and forward . You needn't go mad with it as long as the whole surface is matt when dry. Also don't let it dry out after initial flatting it will leave dried out slurry which is harder than the paint,always rinse it down to get rid of the residue before it has chance to dry then let it dry.

There is a strong risk that there will be contamination of the paint layer especially if you have used a polish,if so it will cause fish eyes to develop ,Really hard to get rid of.So go to an auto paint supplier and ask for a additive to overcome the silicon in the polish <(Forget what its called now think it was conditioner or something like that ) all it takes is a eyedrop amount into the spray can

.If you do get fisheyes don't be tempted to try to rub them out ,all you will do is cut through to the primer and then you have the trouble of sinkage and lifting. Just very lightly flat that area and drop spray pattern down and paint content down to a small very dry out put. then lightly, touch at a time,spot paint the area letting each touch time to dry do it a few times but not enough to cause a high spot ,sometime this works and the fisheyes are covered,sometimes. then you can t cut the dry spray area to a shine.
Glad I'm not involved anymore to busy windsurfing,, kite surfing land yachting, fishing and holidays. ah retirement.

Also if you are just spot repairing ,not the whole panel don't be tempted to mask off round the area mask off a long way back from ,it this stops a line or ring forming in the paint just let the oversrpray land on the outside of area ,then after drying out t cut the overspray out. If you do need to mask off use one or two strips of tape one on top of the other each overlapping to form a cavity underneath ,lift the top edge up to help, this restricts the amount of paint going up to the bottom layer of tape and thereofor doesn't form a ring just a very fine dull area which is easy cut back .
good luck with it

Mark Wilson
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Re: Protecting cellulose

Postby Mark Wilson » Fri Feb 15, 2019 10:44 am

Many thanks. Don't expect to get back to the paint till April, but this is valuable advice.


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