Bongo Fury

Dented my Freda a week after buying it!! Got the dent pulled out, filled the depressions and primed it. Then today I sprayed 5 coats of basecoat - looking good - then 2 coats of lacquer - still looking good - then another coat of lacquer and it dried with the patches shown on the photo below. Can anyone sugges the mistake I must have made - would I be able to rub down the lacquer, spray another coat of base and start again with the lacquer.
Thanks
Ron

http://www.livejazzuk.co.uk/dentprogress005.jpg[/img]

link should be
http://www.livejazzuk.co.uk/dentprogress005.jpg

Looks to me like the paint has bloomed due to cold air -if so -have you tried T- cutting it? Another thought is that the previous coat was not fully dry and hardened before applying the next coat.

Hmmm - tricky this. First off, I think you are bound to get a faint line where the masking tape is if you've let any paint / lacquer get near it. The blook looks odd, like you were spraying in cold air and/or on to cold surfaces. Is it remotely possible it can be persuaded to vanish by (carefully) warming the whole area up with a hot air gun to drive off any moisture? Other than that I'd agree that t-cutting is worth a go. I've just resprayed a compete bumper with total success, but that is easy than just doing a patch of metal like yours, and I was using a decent compressor and gun too. I have one or two dents like yours to fix but am v wary because of the problems (as you are finding) that you can have. V difficult I think to get an invisible patch respray.

Anyway, I'm no expert so with luck someone on BF who actually nows about these things may chip in.

Good luck - at least its not life threatening

A few pointers:

You only mask at panel edges, just blend in as best you can to the middle of the panel. You cant sand a masked edge because you take of the laquer as you feather.

Once you have the surface filled and perfect you need to apply a barrier coat to prevent sinking and reaction. Then you go with a primer, etc.

Feather out the base past the primer and the laquer past the base. To do a good job you should laquer the whole panel once the base is satisfactory.

De-nib with 1500 to 2000 grit paper and polish up with Fareclar G3.

If you are using two pack go with a fast hardner and thinner to try and beat the temperature.

If you are going with celly then get good quality fast, anti-blooming thinners but I doubt you are - it is all but illegal to sell now.

If you are using water based youve bought the wrong stuff.

If you are using acrylic then accept it wont ever look good enough (but OK if your not too fussy).

Patching in a metallic paint is a pain for experienced painters so you will be unlikely to do an invisible repair working at home.

Phew, this man SM knows his stuff. Great this, cos I've done a reasonable amount of 'amateur' spraying and have wondered about most of what SM is saying so this is very reassuring i.e. it is not easy - or nigh on impossible - to do invisible patch repairs like this without top gear, top materials and top skills. Got a few questions for SM:

1) The barrier coat. Not heard of this before, except that I've had to use something like this when spraying cellulose onto a plastic bumper in order to protect it from reacting with the cellulose paint I apply after that. Is there a need for somethign like this over metal too?

2) Will warming the surface to be sprayed, paint to be sprayed etc give you any chance of avoiding blooming (which I presume is a problem in cold/damp weather)

3) Can blooming be teased out of the paint by careful use of a hot air gun

4) More of an observation than a question. I bought a decent compressor and airgun on ebay (got it for £50 in excellent nick, and offset the cost against not getting my bumper repaired by a bodyshop). The difference in what is possible with this and using spray cans (which is what I'd endured before) cannot be overstated. I think I will be able to manage some quite decent patch repairs with this device as I can mist in my paint with a finesse that is inconceivable with cans, or a cheaper / airless gun. I knew I should have bought one years ago.

Mike

Funny thing is I havent done much painting for years but I came out of retirement las month to paint my new kit car. It reminded me how easy painting is with a few exceptions - these are; temperature, dust and colour matching. The quality of the gear is surprisingly unimportant (as long as you have a minimum of a 9cfm compressor).

1) the barrier coat serves two functions, preventing sinking on filled areas and preventing a paint reaction. Even paints of the same type can react at feathered edges and give you a very obvious edge where you swore was smooth before you painted. A filled area will tend to suck back paint and you will notice a faint outline of the filler a few weeks after you thought the paintjob was perfect. Barrier coat fixes both problems but you can't sand through it or you will be back to square one. The answer is to have the area perfect before application. I never put anything on bare metal but etch primer (it contains phosphoric acid which eats in to the metal and keys better) but ordinary primer will do fine on clean rust free metal. Filler works best direct on bare metal, any paintwork under it will increase the chance of it edging at a later date.

Warming the surface is great as long as it stays warm for several hours. I have had to put a radiator under panels to keep them warm and it works fine. An infra red heater is a good option as well. It also helps to prepare the paint in a warm room.

Blooming is unlikely to occur with modern paints (unless it is very damp - just wait for a better day). This used to be a problem with cellulose paints and they are almost illegal now so you probably won't have any. Expensive thinners is the way to go - save the cheap stuff for cleaning the gun. If you do get it you are always going to have milky colour.

Panel wipe is a useful solvent - it avoids fish eyes by removing all contaminants (especially silicones). Use it just before painting.

If the preparation is good the final job will be good. Even if you dont get a good finish from the gun you can flat back and polish to a perfect flat gloss.

I should add that two pack paints contain isocyanates and if you are going to mess on with them get a SOLVENT MASK. Dust masks (even really good expensive ones) are virtually useless.

I agree mike, some good advise there by smartmonkey...

It's a tricky place to do an effective blow-in really ronhud... You are looking at a lot of different angles in that particular spot,with a lot of variations of light. The blooming is there to stay i'm afraid, unless you can wet-flat the surface lightly with 1500-2000 grit wet & dry,then t-cut a sheen back into it. (the blooming may have occured a couple of layers lower though)

If it was my bongo i'd sand it flat, use a bridger primer, then a regular primer,re-apply the neat green, (feathering the edges) then lacquer to the shut line of the boot,the mid swage line of the rear quarter,and then up to the rear side window.

I wouldn't like to chance that amount of lacquer using cans though...

Where do I get this wonderful barrier coat stuff SM? I've certainly found that getting an invisible repair with filler is extremely hard - maybe this will help.

I also remain puzzled about the statement that cellulose paints are 'history', as the tin of Silent Silver I bought recently smells of cellulose thinners pretty much as it used to all those years ago - but is it somehow different?
Good thread this thanks to SM, and BDC who - although he insists he is not - is a bit of a dab hand at a wide range of Bongo tasks.

I get all my stuff from the local car shop that mixes paint. We have two or three specialists in a small area so I guess they are thick on the ground. The barrier coat comes in a ready to spray 1L tin for a tenner or you can get it in aerosols.

The problem with celly paint was the amount of fugitive emissions you get from the spraying process. As far as I was aware the only ones that are still legal are the ones with a high solids content. You need fewer coats so the overall emissions pass the requirements. I think there are two manufacturers left who can supply legal paint. I guess that touch-up cans might be exempt because they aren't used in the regulated industry.

Thanks SM - I'll remember to get soem of that next time.

On the celly paint business, I remain confused (not your fault!). I guess the 'fugitive' bit means 'gets away into the wider environment as vapour / something that doesnt fall to earth in the close vicinity of the job'. So celly solvent would be fugitive and - as you imply - all you can do is improve the amount of sollid content that gets sprayed for each amount of solvent. So I buy myself a tin of said paint and am told to thin it 50/50 with celly thinner. Seems I'm back where we started. You cant help but feel that this is all a case environmental emperors clothes.

The 2-pack lacquer on the other hand does seem to be a different beast. Mix 2:1 ratio in the two tins (to start a chemical 'set' presumably) and thin 10% with celly thinners so it sprays well. If the Silent Silver paint was a similar preparation then I'd understand. I guess it may be that the paint colour matching process is just that more difficult with 2-pack paints so the paint shop I went to wouldn't enter into it and offered celly paint instead.

I wonder if your info above would make a good BF factsheet if there isnt one already. Spray painting is one of the darker arts in Bongo blinging.

mikeonb4c wrote:Where do I get this wonderful barrier coat stuff SM? I've certainly found that getting an invisible repair with filler is extremely hard -

Your local motor factors that mixes your paint should stock the barrier primer mike, or, bridger primer as i call it (dunno if the terminology is correct )

The usual ratio for 2 pack is 100 paint, 50 hardner and 15 thinners as a ratio. Celly thinners works but it makes it harder to get a good job. 2 pack thinners are different and maximise the conditions they will work in. Different types of paint have different mixing ratios. I often add 20 of thinners in colder conditions and to get a flat top coat.

Metallic is a 2 part process with no hardner in the base coat (just thinners). The laquer has the hardner in and sets the base coat off as well.

High build celly paints have more pigment content in the mixed state so you do need fewer coats.

If you are trying to match metallic then you need to play around with air pressure, spraying distance/direction, number of coats, heaviness of coats and temperature to get the closest match. Pearlescents are even more finickity. If I am spraying a fancy paint I always have to do the whole car in one go because you can't always get a match the next day. Obviously an expert in a controlled environment should get it nearly right every time.

I'm more confused than ever.


I'll get me coat.......

Sorry.

If you have any specific questions I will be happy to have a go at them for you but please remember I am only a hobbyist - not a painter. I just used to do a few salvage repairs and restorations as an interest. Mind you some of the proffesional spray jobs Ive seen recently don't take much beating.