Flatting Primer - Wet or Dry?

[tranquilitybase]

I've finally got to the etch primer/primer stage with some front end parts (blasted to bare metal) today. It's two or three decades since I last did any paintwork, so I have been looking on the internet re the next stage in the process. "Maybe things have changed" I wondered??

I decided to check things out as I must have become neurotic about metal going rusty in my old age and I recall that primer is porous. In my search I found various debates about flatting primer wet, vs flatting it dry.

Here's one of the debates...

www.mig-welding.co.uk/forum/threads/dry-sanding-vs-wet-sanding-high-build-primer.22161/

I would appreciate any advice on this please. (I'm starting to think that dry is the way).

Many thanks.....

[tranquilitybase]

Hhhmmm.....Changed my mind...I doubt I'd be able to flat body stopper dry very easily. I might flat wet and then take a hair dryer to it.

Any advice, comments or views would be very welcome.

[rab]

Wet gives a smoother and and better finish .you dont put the top coat on a wet pannel so why would it rust.the only reason tin worm can come through is if you did not fix the problem first

[tranquilitybase]

Yes. I'll probably do what I always did. I was just thinking that, as soon as steel comes in contact with water, and the oxygen in the air, rusting would start. On humid days, have you noticed the discs on your car get a coating of rust within a few hours....But I suppose you can get silly about such things.

Wet is best as far as the flatting process goes as water acts as a lubricant and helps to reduce clogging on the paper.

Thanks for your comment.

[henri]

my routine is ,wash over in rusteze ,leaves a black coat n brush marks ,rub it back 280 grit ,modern grade ,bout 140 0ld, etch prime ,2 coats thick, flat lightly ,wet ,800 new grade, then 2-3 coats primer ,numbers 2/3 flatted not 1, all flatting before topcoat 1500,coats before (2nd out of 3 800),all done with loads of water with washin liquid in,stops cloggin an lubricates givin smoother finish ,after rubbin wash off with a hose or waterin can an a sponge or edge of rubber/cork rubbin block,an loads of washin up liquid/degreaser then loads of clean tap water,better if ya in a "soft water" area, if not washed/sponged off the dust/grit drys to a alkili dust/skin that has to be further flatted off,then dry with a clean cotton old sheet/towel, then with a air gun blast all surfaces cracks/seems/crevices an rag of panel wipe,then repeat with tack cloth, any wet left is lifted out by thinners an isnt enuff to cause bloom ,i usually spray top coats with "anti bloom" thinners just for belts n braces an in case air is damp,
i was taught that by a pro an its never let me down , well wen i stick to it , Henri

[tranquilitybase]

Thanks to all for your advice...

I've been wet flatting today, but not with washing up liquid. Three applications of stopper and being careful not to rub all the primer off. I've been using 600 grit paper. It's getting there but I'm going to give it three more coats of primer next week, and then see what it looks like when flatted again. I'll go over it with 800 grit to finish.

All this for just a mudguard but it looked a real mess before a mate bead blasted it so I'm satisfied with what I've achieved. I'm using it as a practice piece before tackling the frame. I'm just going to give the fork tube and back plate a quick flat and that will do.

Although not ideal, I suppose it's acceptable to flat finish coats, apply stopper, and re-finish if something appears due to sinking (or was missed at an earlier stage) This could be a life-time's work! Good for the soul though.

[henri]

paint prep is always a long boring job ,but the more ya get it right now the better the finish ya can achieve ,good for the soul maybe but hard on the wrists/grip/hands, thats why i bought a electric clarkes orbital sander ,from machine mart 65 quid,dont buy there disc's tho at 30 for 50quid ,my paint supplyer sells all grades at 10 for 50discs , can take a frame back to bare in about 3 hours ,mudgaurd n panels 2, leavin about a hours hand work on corners/fiddly bits , its got to be a random orbital sander others leave marks that will show through paint, an with a polishing bonnet can polish a new paint job in a hour all over , since buying it i almost enjoy/dont hate prep ,Henri

[tranquilitybase]

Yeh Henri. Having the correct tools can make all the difference. I remember going a few times to an ex-neighbour's body shop where he had some amazing air tools including an orbital (DA). He had air chisels that could cut panels off in minutes too.

Incidentally, talking of tools, I bought a Spraymate and quite pleased with it. I've only used it for primer up to now, but it seems fine for the occasional use I need it for. One BIG advantage with HVLP is the small amount of over-spray. I recall how much of this a compressor system can produce and wouldn't want that amount of cr@p everywhere in my garage.

I'm going to flat and polish the finish coat anyway, so I'm sure it will be fine.

Talking of finish coats, I've read that some people put a final coat on with a fair bit more thinners in it than 50:50. I don't recall doing this (although much beer consumed over the years may have washed away this memory) when I did bodywork on cars with a couple of mates in the 80s. Do you do this or just 50:50 all the way through and then 1200 grit/brazing paste to polish at the end?

[henri]

its called a "mist coat" ,bout 60% thinners done very very lightly ,wouldnt reccomend tryin it on ya first job as its very easy to get "thinners pop" were theres loads of little holes in the paint into the base layers were balls/globules of thinners have gathered an then evaporated off leaving a crater, it cant be polished off an ya have to flat back to unscarred paint an re-paint .
am confused by your use of "brazing paste" to polish ,long time since ive brazed but only paste i can think of was flux ,toxic crap you wouldnt want near paint ,if its a old-skool back-street mechanics trick its 1 i havent heard of before .i'd stick with proper rubbing compound ,halfords do a general 1 thats ok,in a yellow toothpaste tube ,or where ya gettin your paint will prob also supply the different grades (rough to fine),you can use t-cut but its a bit aggresive on new paint an ive been told paint has to be at least 6 months old first, ive always stuck with the right compound thats designed for the job too precious about my new paint to risk anything else .an whatever ya do leave it for 2 weeks to harden before wrapping to protect during the build or any moving or it will scar . H

[rab]

i got the exact same orbital from my local machine mart H and it was a god send when it came to sanding down. i found the homebase orbital sanding packs are very good you can get all one grade packs or mixed grades £7 for a pack of 5. price is a bit steep but they do last a while and do there job

[henri]

have to try the homebase ones ,tho the pro 1's from paint shop are pretty awesome, an at 50 sheets for a tenner ,an my daughters elephant waterin can to drip feed the water is brill,goes everywhere so ya got to goggle up,reckon gettin a sander should keep me ridin til im loads older ,got wrists that sound like breakin twigs as is an hand sanding was killin me by inches , almost enjoy it now ,well almost dont mind it so much ,H

[tranquilitybase]

The guy I mentioned (who was the chief sprayer for Knibbs Fiat in Manchester) used to call it brazing paste. This was in the days when I lived in the frozen north. I had a re-union with some mates up there a couple of weeks ago and was reminded how much cheaper eating and drinking is compared to Cambridge (where I live now). Cambridge seems dearer than London. Sorry....ranting again...My wife thinks I'm turning into Victor Meldrew.

My neighbour might have been "having me on" re the term "brazing paste." I've bought the correct stuff, along with the paint etc, from the place you mentioned in Brighton. They seem familiar with people restoring old vehicles.

Good point re letting paint harden fully before flatting and polishing. I'd forgotten about that.

[henri]

prob just a local name, an careful bout the frozen north jokes ,lot of "northen monkeys" on here ,ex pat lancs lad meself ,livin amongst the southern heathen so long people have to listen close to catch it in my voice,down here at the "bottom edge" in brighton the prices are even worse an the locals look down on you yokels/flat-landers up on the east edge,but then they "look down" on everybody .dont worry aint going to reminisce bout the last p##s up north of watford an how it cost 3pence hapenny an a shirt button,
accordin to what ive been told theres a optimun time for polishin ,either 1-2 days no more than a week after last paint/flattin ,longer the better ,def after 2 weeks leave to age 6 months min ,an light/minimum, always movin on ,the more gentle the better the "depth" of finish, H

[tranquilitybase]

Ha Ha.....I like it H.
I'm not knocking northerners by the way...After all, I'm one. Fancy you coming from Lancs! Which part are you from?

Yeh, some people look down on everyone, but when you look carefully, they're stood on a box and are quite small really. Hey, that sounds like something John Lennon would have said....Sorry, we're going off the subject.

Did you come across any 8" wheels by the way H? I probably won't need them for a few months, but if you have any in good nic I'd be interested in buying them off you.

[henri]

i did clear the shed a bit at weekend an looked through the rim-pile ,havent got any good piaggio rims i'm afraid , got a set of 2 aftermarket 1's that would need blasting/wire wheeling an painting ,but honestly there pretty much last legs an i dont think i could put a price on them , if ya need a set to wheel scoot about til ya can find something better they will do for that but postage would kill it , will check my other rims in garage for better ,i havent forgotten ya askin jus been busy,
an i'm born in the pool whilst it was still lancs not merseyside ,moved out with the posh "woolybacks" in maghull when i was young enuff for mum to go snobby an register me in ormskirk registry office . so all south lancs brought up til ten ,but 100% bred in the pool so scouse thru n thru, H

[henri]

check out my answer to ya wanted add ,2 rims piaggio, 25 quid brand new in england ,bargain , H

[tranquilitybase]

My father was a scouser. He lived in Gerard St, which was where many Italian and Irish immigrants lived (he was half Irish, half Italian) and then he lived on Scotland Road. The Pool has changed a lot though.

So, you and I are from within the same area. I spent most of my younger days in Stretford....About 2 miles from Mcr Utd ground. Never been once to a football match though...Can't stand the game. I'm pretty unique with this. Prefer mountaineering.

I can't see your answer in the "Items Wanted" section. When I click on your name a shoutbox comes up with entries about all sorts of things, but not wheels. It's probably me not doing something right.

[tranquilitybase]

Henri,

Thanks for telling me about the rims. Do you think they will definitely fit my Sportique? If so, I will probably bid.

[coaster]

Aug 16, 2014 15:41:32 GMT tranquilitybase said:

Although not ideal, I suppose it's acceptable to flat finish coats, apply stopper, and re-finish if something appears due to sinking (or was missed at an earlier stage) This could be a life-time's work! Good for the soul though.

A lot of good advice from henri, but just to add that when you have finished flatting the primer, use a spray can of a dark colour and apply a very dusty coat. Then flat it off (wet), any imperfections or low spots will hold onto the paint and be clearly visible. Apply stopper or small amount of filler, flat and re-prime. You'll know when the primer is smooth enough as it will have a shine to it when held at an angle.

And don't use T Cut on anything, it contains ammonia and can stain the paint, Feracella G3 for restoring shine after wet flatting followed by something milder. McGuires di a good range od compounds and polishes.

[tranquilitybase]

Many thanks Coaster. The more advice I get on this the better. I appreciate it...

[coaster]

Referring back to the 'with or without water' debate, I think the concern about using water is really for sanding filler. Filler as you may know uses talcum powder as the filling medium held in the resin. The talc absorbs water like a sponge and if primer is applied before it evaporates it will cause micro blisters in any paint sprayed on top. Professionals used to use a product called PSF (Polyester Spray Filler) which was basically a thinned down version of body filler and this was notorious for holding water and micro blistering. Oven baking was often employed to make sure it was good and dry before paint. Fortunately 2 pack filler has the same scratch filling properties (it'll fill 80 grit sanding marks) and it doesn't hold water.

[henri]

agree with coasters take on it , i was taught t-cut is too harsh to use on new paint as its for rejuvenating faded old paint,an paint has to be 6 months old min for t-cut.
an coasters dark colour mist coat i was taught called a "speckle" coat or guide coat ,a matt primer finish can hide loads of faults that will show on gloss top coat , an most flat back n compound the final coat ,i usually leave for 3-4 weeks to harden fully an just use halfords rubbing compound very lightly as you dont want to rub thru an have to re-paint as your outside the optimun 2 weeks new paint layers adhering time ,an shud really wait another month an flat back aggresively an put 2 more coats on then , H

[tranquilitybase]

OK. Thanks to you both.

Rather than the guide coat idea, couldn't you just accept another application of stopper to a finish coat. To be honest, I don't remember using the guide coat method when I worked "under the wing" of the pro chap I mentioned before. He was the chief sprayer for a main agent in Manchester at the time. We did about a dozen re-sprays together including a retoration job on a Jag 420G (like MK10).

[henri]

bet he had other tricks to find low spots , running fingers in cotton gloves over ,sheet of thin paper an run fingers ,bending an c**king his head to catch light at diff angles ,or just so practiced at flatting/prep he could spot the shiny spots in dulled/flatted paint ,
an its your paint job so i'd accept a pot of dulux an yard brush job,its what you want ,every body gets to a point off "it will do" ,wether thats coz its 100% perfect or like me my wrists just wont do anymore prep without seizing its up to you, frankly 95% right is good enuff only other painters will be able to spot it ,an they will have to be close/inspecting it . i do it til i think its ok ,then my missus has a good look ,if she can only spot 3 or less bits i paint it ,use to use my pops but he's a anal-retentive nut job who's got wet n dry paper older than me ,he's a theory the more ya use it the more smoother it is=better finish to paint, to be honest his paint jobs are better than pro standard but couldnt deal with him finding atleast 10-20 faults on every inspection ,
youve got to get to a point where your happy an am sure the topcoat results will do it justice , its a personal thing an one i struggle with so pass the decision to my management/style department (missus). H

[coaster]

Aug 26, 2014 18:58:34 GMT tranquilitybase said:

OK. Thanks to you both.

Rather than the guide coat idea, couldn't you just accept another application of stopper to a finish coat. To be honest, I don't remember using the guide coat method when I worked "under the wing" of the pro chap I mentioned before. He was the chief sprayer for a main agent in Manchester at the time. We did about a dozen re-sprays together including a retoration job on a Jag 420G (like MK10).

Calling it a guide coat is a bit misleading, what you do is put on a 'misting' coat by holding the spray can about 12" to 18" away from the panel. You are not trying to cover, just to cover the panel in a dappled very thin layer which is easy to flat off to 99% of the surface. The remaining 1% will be the odd low spot or pock mark that you have missed. Paining on top of celly stopper is a real bodge and will eventually sink and show through the top coat.

[tranquilitybase]

OK H thanks. I'll get "mission control" to do the quality assurance. That's a good idea. She's a dab hand at spotting my mistakes! A yard brush is a bit crude but I might use a mop and bucket.

Coaster...thanks for the mist coat detail. I was talking to someone recently about the fact that it's virtually impossible to use a block when flatting a scooter. It's obviously not like a car with large, relatively flat areas. So if most of the flatting is done with the paper in your hand/fingers, doesn't this tend to rub all the mist coat off as your fingers will go in the low spots? Sorry to labour this. It would probably be better if I just had a go I suppose. I'll shut up soon.

[coaster]

I would say you can use a block of some sort on probably 70% of most scooters. The inside of the leggies will be one area where you would need a smaller black and the front mudguard would be a fingers only job. I fold the paper a few times for places like recesses in panels and along sharp edges. I spent an hour or sanding down a skim of filler on a PX side panel after first knocking most of the dents out. I sanded using a piece of 3" x 8" timber as I couldn't find either of my rubber sanding blocks and found I could easily do all of the curved surface apart from the recessed strip which required a piece of 1" x 4" batten for the block. I don't see it being any harder when I get on with the wet & dry

[tranquilitybase]

I've just been working on the front mudguard, brake back-plate assy, fork tube and the little bit in the centre of the hub. I'm limiting it to get in the swing of things again.

Good points about making blocks out of wood and folding the paper....Thanks. The simple things are easily overlooked.

[henri]

any decorating shop or 99p store will have cork sanding blocks ,there easy to cut-down for fiddly bits ,where its fingers or nothing fold paper an keep fingers at 90degrees to direction of rubbing an as flat as poss ,have tried a cork tile (bendy) for inside leggys once but didnt really get massively better results than fingers an it was fiddly to grip, using washing up liquid in water lubricates the paper so less likely to clog an also less grabby of the paint so doesnt pull out from under block/fingers so much , H

[tranquilitybase]

OK H, thanks for the block ideas. I need to experiment.

I seem to remember reading that you shouldn't use washing up liquid to wash your car because it has salt in it. I wonder if this could have an adverse effect on the prep stages? I was about to rant about everything having salt and sugar in it, but have managed to control the Victor Meldrew in me.