Micro-blistering of 30 year old cellulose on 'Mary Ellen'

[Tony Fearn]

I'm in the middle of using Nitromors to remove the cellulose paint from the rear half of 'Mary Ellen'. She's suffering from micro-blistering of the paint work, both on the steel panels below the waistline, and the aluminium panels around the rear and back windows above the waistline.

I've only yet got down to the steel panels, but there are myriads of tiny rust spots showing up after removing the cellulose base coat. I realise that these will have to be sorted out, but perhaps Chris can reply with the best way to go on from now.

I have already bought etch primer, high-build cellulose undercoat and the top black cellulose finishing coat, but would rather know how to sort the rust problem out before I spend time spraying all this.

The last time I sprayed the car was in 1980, so the cellulose has lasted quite well over the last 30-odd years. Prior to that my mum and I hand painted it with Tekaloid enamel in the early 60's!!

I can take a photo of the problem if that will help Chris, (or anyone else that wishes to comment). I mention Chris because somewhere in the 'little grey cells' I remember he's been there, done that, and has offered his expertise within JowettTalk, which will benefit us all.

If the new paintwork lasts another 32 years, then I'll be getting a certificate from the Queen on March 11th of that year!!!

Tony.

[Chris Spencer]

Hi Tony - Yes I very much have several T shirts in the micro blistering department - so that everyone can learn what the root cause is and how to resolve the issue - please could you post a couple of images - one of the micro blistering - before / after stripping if possible - I will then go through the step by step process of resolving the issue.

Regards

Chris

[Tony Fearn]

Hi Chris,

I've attached a rather indistinct photo of the scuttle paint (black cellulose, with fluorescent light reflections) which, with some imagination shows the micro-blistering. It feels like braille when you run your fingers over it.

The other photos are of panels stripped of the black cellulose and partially stripped of the primer/filler coats.

Tony.

[Keith Andrews]

Why continue to use cellelose, that stuff was basically obsolete by the late 60s early 70s.
Then lacquer came into vogue.
Cellelose is only used for ladieis fingernail polish these days.

Prep of steel no mater what system one uses is citical...and materials/ pre for modern materials has also dramtically changes
Get the car back to steel...
never let steel sit open to the air more than 20 mins after prep...
seal it with either phosphoric acid...(rust killer) and I recomend Annitrol.. doent have additives....or better still epoxy.
Those rust pits should be scuffed out (scotchbrite works well) then finished with Annitrol, let dry and epoxy.

Any filler that maybe needed (ie this rust pits) is the APPLIED OVER the epoxy.. not directly to the steel.The old school of any filler direct to sreel went out the window many years ago.

After filler goes the high build under coats, blocked back but NEVER go thru the epoxy layer... never.
The high build should be of a type that is compatable with the final coats....
2 to 3 block backs usually gets a car super straight...never use sand paper in the hand,or hand size sanding blocks.. even on curves....flexable blocking boards, and I prefer to use boards as long as practical for the panel being worked on.

With laquer/ enamel type undercoats that rely on solvent evaporation rather than catlyitic hardening, leave a coat at least a week before blocking...depends on how straight u want those panels in 12 months time.

Etch prime technology went out the door 20+ yrs ago.

[k. rogers]

I don't understand why people are so against cellulose, other than the time consuming element and that it is less forgiving than modern 2 pack. To me it is the only practical paint for the home restorer who doesn't have bake facilities and the respiritory gear required. Actually, I prefer the finish that can be achieved with cellulose and it is the case that the more effort you put in the better the finish - also it suits our old cars much better, I think, not only in appearance but in durability. You can also do spot repairs which will blend in well as opposed to having to paint the whole panel!

[Keith Andrews]

I don't understand why people are so against cellulose, other than the time consuming element and that it is less forgiving than modern 2 pack. To me it is the only practical paint for the home restorer who doesn't have bake facilities and the respiritory gear required

Why continue to use cellelose, that stuff was basically obsolete by the late 60s early 70s.
Then lacquer came into vogue.
Cellelose is only used for ladieis fingernail polish these days.

Are u sure that you are not confusing the old cellelose of the 50/60s with the lacquer paints of the 70s and 80s.
yes they handle and lay on very similar, but very different in their make up.
lacqueur these days is frowned upon by many. but I fully agree, for the home paint without a booth , resperatory gear for isocyanates, laqueur is the way to go....in fact Im seriously considering going that way on my next rebuild......again.
Its far more forgiving than 2 pots and enamels when laying down, very hard to get it to run or sag.
Dries very quick between coats...eliminates ovenight drying off as with enamels.
But the down side , unlike enamels and 2 pots, since it does tack off fast, it doesnt flow out to a full gloss finish .
It requires blocking back back with wet and dry, and cutting.....and a must, espec if eridessenent, have at least 2 coats of generous coat of clear over the top to cut back smooth with.
It is very prone over long periods to crazy cracking if has old coats of paint underneath...it best to take back to stell and prepare as I describe above.
It is also very prone, even after seal coats, to attacking any other paint types that maybe under neath..what we call fry up... looks like paint stripper spilt on the paint....

yes laquar is the ideal paint system for the home painter.

[k. rogers]

Sorry, I misunderstood! we must be talking about the same thing - we still call it cellulose here, rightly or wrongly - am I correct in thinking it's full name is nitrocellulose lacquer?

[Keith Andrews]

am I correct in thinking it's full name is nitrocellulose lacquer?

No..
Have a look about 1/2 way down this page
u will see the nitro stuff and the acrylic laquer stuff...Im talking about the latter
http://www.thecoatingstore.com/Types_of_Car_Paint.html
it does talk about cutting inbetween coats..dont have to, and never cut a eridessent paint...ALWAYS put a clear over and then block/cut the clear back to a mirror finish... 100% nill orange peel..
basiclly for the finishes we want... simply a 1st base coat.. just thick enough to see thru , no more....then straight into the next coat, so cant see thru... just... then 3rd coat to make sure good even coverage and a little more retarder/ thinners to slow the final tack off so paint has a few more minutes to flow out...less orange peel ....the previous coats have tacked off enough to stop the next coats saging/ run.
Then leave for about 1/2 to 3/4 hr... hit with the clear coats...2 damn good coats so they are just hanging there without saging or running...
leave a good week
hit it with 1200 wet and dry... not quite taking out all the orange peel... hit with 1600, taking out the orange peel.. then 1800 ....which for many would just need a polish.... other would fine machine cut and polish a few months later...
depends how much time u have on your hands.lol

alway 'clear' laquer

[Chris Spencer]

Ok - Lets first deal with the different paints and their pro / cons:

2 Pack - Is a paint mixed with a hardner prior to spraying - it is very good - requires minimal preperation - drys quickly - and is used extensively within the motor trade - if you do not have dust free, correctly vented spraybooth & the correct air fed respirator - do not use it at home !!

Water based - Is gaining ground and is used in the production of all new vehicles - the primer & colour coats are water based - the final sealer / lacquer coat is 2 pack - again if you do not have the correct dust free, vented, drying & respirator facilities - do not use at home !!

Enamel paints - often refered to as 'coach paint' the old version was oil based whereby the newer versions are aycrillic based - can be sprayed or brush painted and air dried - extensivley used on commerical vehicles & early coach built cars - takes some time to dry but with care a good finish can be obtained

Cellulose - the paint is thinned prior to spraying - requires high quality preperation - but very high quality mirror finishes can be achived - still used throughout the UK

Base coat & lacquer - (what Keith has highlighted) - colour coat with a lacquer applied over - very simular to cellulose preperation & application and can be used at home.

More information to follow today on how to deal with Tonys problem

[Chris Spencer]

Ok - micro blistering - the cause is moisture trapped between the primer and the final paint coats - always remember that primer is porous and will absorb water - if the panel is not completly dry then micro blistering will appear at some stage - sometimes presenting itself within a few hours of painting and then again as in Tonys case - many years later.

The correct action has already commenced - although drastic - the only way to resolve the issue is to bare metal the surface, once stripped of paint the metal will require sanding to provide a key for the paint and to remove as much of the surface rust as possible - use the finest grade of abrasive that you can without giving yourself too much of a task to undertake this - deep score lines from surface preperation just mean more work through the primer stages.

When sanding back / flatting - always use a block on flat surfaces and try to get into the habit of sanding in one direction - from front to back - or vice versa - never in cross directions or circles.

It is important that the rust is neutralised once you have prepared the panel - I recommend Bilt Hamber Hydrate 80 - link here : http://www.bilthamber.com/paints-and-co ... hydrate-80

You can now apply the etching primer prior to the filling of any minor surface defects - with the defects dealt with I would recoat the panel with etching primer again to catch any areas that may have brought to bare metal in the filling process - once complete you can apply the primer - I would always recommend a high build primer filler.

Try to get into good habits and do not rush - you will only reget it later - wiping the panels with a spirit wipe (available from bodyshop suppliers / motor factors) before every paint application is always good practice and will save you a lot of heartache.

Once the primer is dry apply a very light mist coat - matt black areosol is fine - just so that you gain a speckled finish over the primer - this gives a guide coat as you flat the primer back - if you can still see black specks of paint in the primer - then it needs more work - the black will also highlight minor defects - which can be caught with a cellulose stopper - again use the guide coat over the stopper prior to rubbing down - remember the one direction rubbing down routine - front to back through all of the primer / stopper stages - I would recommend repriming a panel where stopper has been used.

Always dry the panel as you go - working on a warm day helps - use a blow gun with the compressor to force the water out from under joints / seams masking etc - and remask if required where the tape / paper has become wet - better that than the masking fly into the wet paint while you are spraying. If the weather is not with you try using a fan heater to warm the panel slightly and ensure that it is dry.

Once complete with the priming stages you are ready for the colour - take your time and apply several coats to build the depth up - if you are getting a heavy orange peel finish try thinning the paint a little more - if you are getting sags / runs the paint is a little thin. Once painted leave it alone - do not be tempted to demask the car too early or start refitting trim - leave it at least 24 hours.

I like to leave cellulose at least 2 weeks + before polishing - flat back using 1800 - 2000 minimum grade wet & dry with a little soap and plenty of water - always use a block on flat surfaces and remember the one direction trick - take care not to rub through on the edges / profiles etc. When flatted you should have a dull surface - you are only aiming to remove the minimum so do not get carried away - next you can commence with the compounding - a medium grade G3 will do the trick (bodyshop supplier / motor factor will stock this but you can also buy on line nowdays) - keep up with the one direction routine - you should start to see some finish coming to the paint - you can use a damp cloth with the compound as you complete the process - always change the cloths on a regular basis - every couple of panels or so - you will find mutton cloth / stockingete the best material to use as it retains the polish within the weave mesh. A T Cut type - finer polish should be used once the compound work is complete - Has with all polishing just do a small area at a time - 300 x 300 mm / 12 x 12" is ample - and stick to one panel at a time - still with the one direction trick - again you can damp the cloth towards the end T Cutting to thin out / fine up the cutting process. Once complete a good quaility wax should leave you with a mirror glass finish.

I have used all paints in a proffesional capacity that are mentioned in my previous posting - I realise that times & materials have moved on since a perfectionist old boy learnt me the ropes some 35 years ago (we were never allowed to machine polish paintwork - it was all by hand) - the celloluse paint system is hard work - you need to remain focused / methodical and take your time - but for me there is no better system for getting the paint to look right on vintage / classic vehicles and somehow the traditional methods fit in with the end product.

Tony - just post up any issues or further questions and I will get back to you - good luck - Chris

[Tony Fearn]

The correct action has already commenced - although drastic - the only way to resolve the issue is to bare metal the surface.

Thanks indeed Chris for the comprehensive and considered replies. Just what I needed.

As you can see below, I'm "drastically resolving the issue".

Just a thought Chris, the aluminium panel won't need the de-ruster will it?

Tony.

[Chris Spencer]

Tony - The aluminium panel will not require the deruster - if you can could you post a few images of the progress / process stages - so that it can be used as guide for other members brave enough to undertake cellulose paintwork on their car - that would be great but do not worry if not as I intend to put a detailed paint process guide together on JT once I get on to the paintwork of Peter Pfisters Javelin which is over here for restoration - just need to get the welding on it completed first.

[Chris Spencer]

Hi Tony - How is the paintwork challenge going ?

[Tony Fearn]

Hello Chris,

I managed to get all the paint off the steel panels with Nitromors and a lot of elbow grease before I went on holiday to Majorca, on 4th Sept., and I brush-painted the panels twice with Hydrate 80 as you suggested. It would have given a better finish to spray the anti-rust agent, but because I never got a lovely dry and sunny day, I did it panel by panel.

Unfortunately there are brush marks over all the panels, but with a bit of dry-flatting and lots of high-build primer as the next job, I'm hoping to get a reasonable finish prior to applying the top coats.

I've only been back a week, and weather-wise it hasn't been fit to do any more, so I'm glad the Hydrate 80 sealant is on. I'll probably have to wait now until May or so next year to carry on, unless we get a week's worth of an Indian Summer.

I've left the original primer on the aluminium until work starts again, although if I take it back to the metal it shouldn't pose too much of a problem over the winter.

Tony.

[Tony Fearn]

Hello again Chris.

I managed a bit more paint removal on the aluminium rear/upper body on Thursday as it was a bright but cold day up here in Lancashire. I have the necessary to etch prime it, but as it's still only about 5 Centigrade, and I have to spray outside, I thought I'd wait to start the spraying until it gets a bit warmer.

What's the minimum outside temperature I'll need to get a good finish, maybe only with the etch primer and the cellulose base coat? I thought of warming the paint pots in hot water to facilitate spraying, but then the spray would be going on to a cold metal surface, so I'm hanging fire.

I'll do the final colour coats in the early summer, after the petals of the cherry tree have all fallen off!!