I have heard a few differing opinions on wet sanding primer, some say it gives a better finish, some say primer (porus) and water are a no go, whats everyone here think? currently the car has been sanded with 400 dry.
opinions on wet sanding primer
Started by
makka
, Dec 27 2007 09:18 PM
22 replies to this topic
#1
makka
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Posted 27 December 2007 - 09:18 PM
#2
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Posted 27 December 2007 - 09:21 PM
I think you will find to get a decent finish for your colour, you will need to wet sand the last coaat of primer and I would be going less than 400
#3
FastEHHolden
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Posted 27 December 2007 - 09:22 PM
I am no expert..but I reckon wet sanding is easier..but i can see that if the panel retains ANY moisture its going to stuff it up.....I heat my panels after sanding the primer...the last bonnet i did..I didn't heat..and its an abortion.
#4
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Posted 27 December 2007 - 09:32 PM
I find blowing down well with compressed air after wet sanding good enough but i much prefer dry sanding primer, i hate the slop and i can see the lows better.
You may want to go finer than 400 (at least 600 to 800) for a final rub especially if using acrylic as the rub marks (scratches) will show thru the top coat.
You may want to go finer than 400 (at least 600 to 800) for a final rub especially if using acrylic as the rub marks (scratches) will show thru the top coat.
Edited by ALX76, 27 December 2007 - 09:32 PM.
#5
makka
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Posted 27 December 2007 - 10:14 PM
I know I will need to go finer but right now I am at that point where I need to decide if I will go finer with wet or finer with dry. If I was to go with wet I would be rolling the car out into the sun and letting it dry really well.I find blowing down well with compressed air after wet sanding good enough but i much prefer dry sanding primer, i hate the slop and i can see the lows better.
You may want to go finer than 400 (at least 600 to 800) for a final rub especially if using acrylic as the rub marks (scratches) will show thru the top coat.
painting it 2k as well, not acrylic
#6
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Posted 27 December 2007 - 10:27 PM
Sounds like your on the right track, more of a personal preference i think, not sure if finer than 600 comes in dry anyway.
#7
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Posted 27 December 2007 - 10:40 PM
400 dry is equivalent to around 600wet.
If it is 2K primer then you won't have any worries of it being "porus" (which is the new term everybody seems to have latched onto to scare others).
I would personally finish off with 800wet with 2K, if your feeling adventurous you could go up to 1000 but I don't think it's necessary.
All you'll need to do is keep an eye out for any "Block" marks, maybe even when your finishing off use a softblock to back up your paper and go over the car lightly to even it up.
Run of the mill paint repairs in a workshop environment typically use 400dry and then 500dry with an Interface pad on a DA to clear up any block marks, BUT that is more for a seasoned painter with plenty of confidence.
If it is 2K primer then you won't have any worries of it being "porus" (which is the new term everybody seems to have latched onto to scare others).
I would personally finish off with 800wet with 2K, if your feeling adventurous you could go up to 1000 but I don't think it's necessary.
All you'll need to do is keep an eye out for any "Block" marks, maybe even when your finishing off use a softblock to back up your paper and go over the car lightly to even it up.
Run of the mill paint repairs in a workshop environment typically use 400dry and then 500dry with an Interface pad on a DA to clear up any block marks, BUT that is more for a seasoned painter with plenty of confidence.
#8
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Posted 27 December 2007 - 11:23 PM
Please, go on, I am enthralled!If it is 2K primer then you won't have any worries of it being "porus"
#9
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Posted 28 December 2007 - 02:50 PM
Please, go on, I am enthralled!
Now being the internet it's a little hard for me to determine if this is pure sarcasm or not??....I'm going to give the benefit of the doubt and of course explain my reasoning in my previous post.
I'll start by confirming...YES, ALL PRIMERS ARE PORUS, this is a well known fact. There is no way I would recommend bare metalling your car and then painting it in primer and leaving it outside in the rain for 12months. Moisture will get under any primer and rust your car. I'm glad thats out of the way.
2 pack Primer/Putty contains much higher Solids content than any Acrylic Lacquer Primer ever did. Consisting of two parts (Paint and Hardener) gives a much stronger chemical composition compared to the old Acrylic which relied on the solvents (thinners) evaporating to cure. These means the Paint surface will be inherently stronger and if you apply it correctly (typically 4 wet coats with correct flash off times) the substrate (ie. your cars body) will be adequately sealed.
Wet Rubbing a car is a proven technique, anyone who has ever had moisture problems arise in their finished paint surface is looking in the wrong direction if they are going to blame wet rubbing for the result. More than likely it was poor initial surface preparation or water in their compressed air supply when they have painted it.
After you have wet rubbed your car it is good practice to do as the other guys have mentioned and blow it down with compressed air and also leave it in the sun for a few hours to make sure the surface is dry.
Like they say "A little bit of knowledge can be dangerous"...It's always best to ask as many questions and try and learn as much as you can on a subject and learn from others mistakes (which we all make). It's great nowdays with the internet that you can find plenty of information on any given topic.
Who knows?? We all might learn something!!
#10
rodomo
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Posted 28 December 2007 - 04:48 PM
This isn't sarcasm Pete, it's more like paranoia in Heath's case.Please, go on, I am enthralled!If it is 2K primer then you won't have any worries of it being "porus"
He's working in a carport and his car gets wet in the rain.
#11
_Bomber Watson_
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Posted 28 December 2007 - 05:45 PM
Told you Heath.
Im not a proper painter, but i do paint drill rigs for a crust.
We get stuff sandblasted, then i give it a flick of 2K primer and it goes off and sits down the back for quiet a while.
Usually it takes at least 6 months for surface rust to start appearing.
Thats crap primer and only 1-2 coats.
Wet rubbing is fine boys.
Im not a proper painter, but i do paint drill rigs for a crust.
We get stuff sandblasted, then i give it a flick of 2K primer and it goes off and sits down the back for quiet a while.
Usually it takes at least 6 months for surface rust to start appearing.
Thats crap primer and only 1-2 coats.
Wet rubbing is fine boys.
#12
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Posted 28 December 2007 - 09:01 PM
Pete, I thought it was the other way. Dry paper is twice as abrasive as wet, so wouldn't 400 dry be the same as using 200 wet?
Cohen, I wet sand my primer, and no issues to date.
Cohen, I wet sand my primer, and no issues to date.
#13
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Posted 29 December 2007 - 01:19 PM
You might be thinking of Fastcut Dry Paper which you normally use to sand down Bog etc.
The normal Dry rub sandpaper is normally a finer finish.
The normal Dry rub sandpaper is normally a finer finish.
#14
_Yella SLuR_
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Posted 30 December 2007 - 10:01 AM
Pete,
Can you make a new topic on sanding and put some pointers down, i.e. types of sandpaper, and tips/tricks to getting a good finish? I think this area is most often overlooked, but most vital to a good paint finish.
Can you make a new topic on sanding and put some pointers down, i.e. types of sandpaper, and tips/tricks to getting a good finish? I think this area is most often overlooked, but most vital to a good paint finish.
#15
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Posted 30 December 2007 - 11:05 AM
i always wetsand but I do it out in the sun, when we have it....
#16
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Posted 30 December 2007 - 11:47 AM
I've got a couple of LH/LX guards here that I might do a bit of a Start to Finish "How-To" from Baremetalling, Rust repairs and panel work, priming and then painting.
It might take me a little while to get through as time is scarce but I think it would be cool. Everyone has their own way of doing things so it will make a good conversation piece.
It might take me a little while to get through as time is scarce but I think it would be cool. Everyone has their own way of doing things so it will make a good conversation piece.
#17
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Posted 30 December 2007 - 11:56 AM
It might bust a few myths tooIt might take me a little while to get through as time is scarce but I think it would be cool. Everyone has their own way of doing things so it will make a good conversation piece.
#18
_HatchmanSS76_
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Posted 30 December 2007 - 12:05 PM
That would be awsome Pete and much appriciated by so manyI've got a couple of LH/LX guards here that I might do a bit of a Start to Finish "How-To" from Baremetalling, Rust repairs and panel work, priming and then painting.
It might take me a little while to get through as time is scarce but I think it would be cool. Everyone has their own way of doing things so it will make a good conversation piece.
#19
_tazidvl_
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Posted 06 January 2008 - 10:43 PM
May be some you tube vids to explain the process but thats asking a lot. Would be good though.I've got a couple of LH/LX guards here that I might do a bit of a Start to Finish "How-To" from Baremetalling, Rust repairs and panel work, priming and then painting.
It might take me a little while to get through as time is scarce but I think it would be cool. Everyone has their own way of doing things so it will make a good conversation piece.
#20
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Posted 06 January 2008 - 10:48 PM
I've started on a guard, and taken some pics and started writing, Weather/Family/Injured Dog have slowed me down this week but hopefully will have something up in the next few days to kick off the conversations!! Should be fun.
#21
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Posted 06 January 2008 - 11:15 PM
i cant wait, as i have a lj gtr about to get sandblasted, then i have to etch prime it, then the fun begins, body work, it would be great to get more pointers as i am no expert but willing to have a crack!
#22
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Posted 09 January 2008 - 08:40 PM
ived used dupont epoxy primer after stripping back to bare metal and then
using a guide coat and a speed file with 120 grit sanded down to find lows and using a hammer and dolly worked them up, guide coating and sanding to see where im at,then gave a light skim of niki over quater guide coated and sanded down until there was no ripples or low spots left,dupont make a epoxy primer that you can do your repairs over and then hifill and guide coat and rub back again using the speed file with 180 grit, then hi fill again same again but just take guide coat of with the 180 then go down to 240 grit dry or free cut paper what ever you what to call it,then once im happy with it (check to see if its straight or like bondi beach)ill rub with 800 wet using little amounts of water,then re guide coat and finish with 1000 grit wet paper and ready to paint,i find it hard to explain,but easier to show people as well,it is alot of work invovled repairing a car that has been stripped back to bare metal and to make sure its done properly aswell,the better your preperation is the better job you will get, you take short cuts they will come back and bite you in the arse
using a guide coat and a speed file with 120 grit sanded down to find lows and using a hammer and dolly worked them up, guide coating and sanding to see where im at,then gave a light skim of niki over quater guide coated and sanded down until there was no ripples or low spots left,dupont make a epoxy primer that you can do your repairs over and then hifill and guide coat and rub back again using the speed file with 180 grit, then hi fill again same again but just take guide coat of with the 180 then go down to 240 grit dry or free cut paper what ever you what to call it,then once im happy with it (check to see if its straight or like bondi beach)ill rub with 800 wet using little amounts of water,then re guide coat and finish with 1000 grit wet paper and ready to paint,i find it hard to explain,but easier to show people as well,it is alot of work invovled repairing a car that has been stripped back to bare metal and to make sure its done properly aswell,the better your preperation is the better job you will get, you take short cuts they will come back and bite you in the arse
#23
turbotrana
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Posted 19 January 2008 - 02:56 PM
I am no expert in painting but there are issues with wet sanding. They mainly revolve around leaving tap water drying on top of the surface to be painted.
I will explain as follows. When it rain falls on your cars paintwork, you can leave your car out to dry when the sun comes out and it leaves no water marks.
However in areas of heavy tap water or even ordinary tap water, if you dont dry off the water dropletts off your newly washed paintwork you can seen water marks left behind.
So when you do wet sanding you must hand dry the surface and even splash a bit of distilled water on the surface to get rid of all the salts and minerals being left behind whilst the water has evaporated.
I know with acrylic painting that when you paint over the mineral and salts that it does show thru over time. It may take many years however with two pac I dont think it would show.
Also primer is porous and whilst the surface may appear dry, it may still have water trapped in the surface. So if you wet sand and then paint 30min later with it just looking dry dont be surprised if years later the surface has crows feet cracks.
I will explain as follows. When it rain falls on your cars paintwork, you can leave your car out to dry when the sun comes out and it leaves no water marks.
However in areas of heavy tap water or even ordinary tap water, if you dont dry off the water dropletts off your newly washed paintwork you can seen water marks left behind.
So when you do wet sanding you must hand dry the surface and even splash a bit of distilled water on the surface to get rid of all the salts and minerals being left behind whilst the water has evaporated.
I know with acrylic painting that when you paint over the mineral and salts that it does show thru over time. It may take many years however with two pac I dont think it would show.
Also primer is porous and whilst the surface may appear dry, it may still have water trapped in the surface. So if you wet sand and then paint 30min later with it just looking dry dont be surprised if years later the surface has crows feet cracks.
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