Omni MBC ( magnetic/metallic) Wet Sanding or not.

[jeff53]

Okay guys- time for another - greenhorn/novice/beginner ameturist basic question.... ( a  little update 1st)  and the price was right around 5k nut they wouldn't be able to do my car in pieces. So I had to figure away to put the urethane paint on myself., if anyone followed I was worried about my asthma and the fumes and I was left with doing the car....but the pro started in urethane so I had a choice either continue with urethane-which has a ton of fumes/ or finish with rattle cans or take it to a Maaco 80 miles away. After talking to Maaco my only feasible choice was  try and do it myself. Now here's where you guys come in coz  it seems you're all pretty knowledgeable and know your stuff cause most of you seem to actually work on or paint your cars yourself. 1st what help my breathing was double up on the masks-- I put on a mask that had those 2 filters on top of the little dust type mask. 2nd was  mix my 2-3 quarts together so they would have the same color. 3rd Since I was worried about pot life--- I just didn't mix as much all at once-- Ie.. instead of 8 oz of paint and 8 oz reducer I cut it down to 4 oz. of each and that covered an area- it took longer. and there  is some do over areas. Here's where you guys come in.... The paint is Omni MBC ( magnetic) urethane base coat a 1:1 mixture. I call it metallic.... Now no need to tell me what I should have used because the Pro started with Omni MBC.  So Just like locksmithing I try to stick with the same brand all the way thru a job even though other brands might work. Question is there are websites that "DO NOT" recommend "WET SANDING" for a nice finish and suggest put on the "CLEAR COAT" and then WET SAND. Automotive paint supply place said next I "DO" want to WET SAND 1st and Then apply the Clear Coat and wet sand it also. and the other sites suggest 'DRY" sand it with 800-1200 grit and put on the clear coat and buff and polish.... What say you? I should add I can "wet sand" but only by way off using a bucket.. I can't hose it down at this point.

 

[Graham Man]

I would get the spec sheets from Omni, they will specify every step including every approved product (normally all Omni products) the paint store that sold you the paint should have all the literature.  I do not remember ever using traditional wet sanding between color coat and clear, only a green scuff pad before clear (it is pretty hard to run color coat).  If you have runs in your color coat you will need to sand them out before clear.  Personally I would repaint the panel with color after sanding, then scuff for clear. 

 

You might want to set up a test panel to practice the clear coat on, my first clear coat hood, went right from runs to tidal wave!  Good clear coat is an art form, wet sanding is a lot of work.  Some systems you need to wet sand within 24 hours or it is too hard to sand ever! it will barely scratch (again the OMNI literature is your friend).

 

Good luck

[jeff53]

56 minutes ago, Graham Man said:

I would get the spec sheets from Omni, they will specify every step including every approved product (normally all Omni products) the paint store that sold you the paint should have all the literature.  I do not remember ever using traditional wet sanding between color coat and clear, only a green scuff pad before clear (it is pretty hard to run color coat).  If you have runs in your color coat you will need to sand them out before clear.  Personally I would repaint the panel with color after sanding, then scuff for clear. 

 

You might want to set up a test panel to practice the clear coat on, my first clear coat hood, went right from runs to tidal wave!  Good clear coat is an art form, wet sanding is a lot of work.  Some systems you need to wet sand within 24 hours or it is too hard to sand ever! it will barely scratch (again the OMNI literature is your friend).

 

Good luck

I do have the Omni Spec sheet and it says nothing about "wet or dry sanding" just the dry times between coats.

[Guest]

 When you sand metallic paint you will sand the little flakes of metallic and change the effect of the paint.

 You will have little gray specs where you took off the color that was covering the flake.

 If you must sand, you must recoat that area, then clear.

[Frank DuVal]

In the old days (80/90s) if you sanded the base coat then cleared, you Would see your sanding marks under the clear. Do not know if new superfine sandpaper has negated that. 

[Graham Man]

I would call the paint shop and ask for the "paint guy" he will know or they will give you the Omni representatives phone number to call.  

[nickelroadster]

I will strongly agree with those who say "do not wet sand the color coat".  I hope you did not put it on too heavy and get streaks in it.  Most base coats do not need to be applied very heavy. If you did, you will have to respray those areas.  I would not even use a scuff pad on the color.  Just use a nice fresh tack rag.

[TAKerry]

I would check with you supplier rather than the written spec. 

I have limited experience painting but what I have done to date has turned out pretty darn good. 

I do not know the brand you are referring to, but I surmise they are all the same more or less. I was told by my paint supplier, as well as from others 'in the know' how to apply and have followed their advice with good luck.

 

I spray the base coat, several coats waiting for the flash time as directed from the manufacturer usually something like 15 minutes between coats. 

THEN, I spray several coats of clear, again waiting on the flash time. 

 

I have been told to spray the clear directly on top of the base coat once it has set up according to specs. Usually within an hour or less. I DO NOT do any sanding at all between base and clear. 

 

I was told NOT to sand at that point. HOWEVER, if the base coat sits for any length of time then very fine wet sanding is recommended before the clear goes on. From what you are describing I think you would fit into the latter category.

[JustDave]

O.k.

to start with you are using a solvent base base coat clear coat,you have already sprayed the base,i it wherei,I would take and stick sand the car thoroughly with 800 grit wet and dry wet of course make sure you get every spot every edge,then after drying and cleaning thoroughly I would put three coats of base color then three to four coats of clear coat,wait about two to three days then lightly wet sand with 800 grit wet and dry,wait two,three or four weeks and water sand with 1200 grit,do not sand with your fingers,take two paint stirring sticks and glue them together,then cut them to about six to eight inches,take and rub them on a clean spot on the garage floor until flat,wrap the 1200 grit paper around the sticks,I know this sounds silly but if you use bottled water yourfinish will be better,machinepolish hand polish wash wax,and on to the next step

[jeff53]

 And there in is the problem-- Look at your 1st line and then the last 2 and re-read... You suggest follow the suppliers advice-- Okay but then your bottom statements--  read just as I have said---- I do NOT sand at all in between base and clear.... My question -if you re-read says this is why I was asking to begin with... My supplier says " Do Wet Sand in BETWEEN base and clear---- and you and other websites say " DO NOT  SAND IN BETWEEN" base and clear... So I'm looking for someone familiar with the OMNI MBC brand. But thanks for your reply... right now- I'm guessing "I SHOULD NOT WET SAND" in between coats--- I just wanted to dbl check before ruining what I have done so far.

[Graham Man]

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[jeff53]

1 hour ago, JustDave said:

O.k.

to start with you are using a solvent base base coat clear coat,you have already sprayed the base,i it wherei,I would take and stick sand the car thoroughly with 800 grit wet and dry wet of course make sure you get every spot every edge,then after drying and cleaning thoroughly I would put three coats of base color then three to four coats of clear coat,wait about two to three days then lightly wet sand with 800 grit wet and dry,wait two,three or four weeks and water sand with 1200 grit,do not sand with your fingers,take two paint stirring sticks and glue them together,then cut them to about six to eight inches,take and rub them on a clean spot on the garage floor until flat,wrap the 1200 grit paper around the sticks,I know this sounds silly but if you use bottled water yourfinish will be better,machinepolish hand polish wash wax,and on to the next step

 Just Dave -- you're either joking or  more experienced than everyone and have your own shop. " Stick Sand- rub them on a clean spot on the garage floor--- really???  I have been and lived in 5 or more states ---and have yet to read or hear anyone " recommend" what you suggest....Must be a trick you learned a long time ago... I'll do all that at the same time I find the place where my turn signal fluid goes. But hey, thanks for the " if all else fails- goto trick". Oh at 67 and 1 back surgery ( years ago) how many times will I need to find a clean spot on my garage floor,'48 4 door is a pretty big tank.

[jeff53]

 Okay guys,thanks a lot, and I'll lean into your suggestions of " Do Not Sand In Between the base and clear coats. This is why I come to you guys. 

   Next and last question on painting---- Keep in mind this is metallic base coat Omni MBC urethane. I'm working with and not a solid color. Recommended Flash time is 5-10 min between coats and 20 minutes min.- to 24 hours maximum- to clear coat ( per Omni tech sheet) Question If I
can't put the clear on right away or within 24 hours"-- then what??? Reason I ask- is everyone states/says I'll ruin or move the metallic "If I have to sand"... 

   Is there a sanding method where I "won't mess up the metallic? If you don't understand the question please let me know and I'll re write it.... I ask this because I'm about to put the final base coat on today and don't see where I would be able to have the time to put the base and clear on in the same 24 hrs ( at least no time soon.. Maybe you guys can tell me if this'll work--- The car is being painted 2 tone-- what I'm doing now is just the top. and I was planning on completing it 1st all the way to clear- then start on the bottom 1/2 and doing the same and "then reassemble the car"( remember it's in pieces) or should I go ahead take care of the bottom 1./2 and then re assemble the car and then put the clear on ( since I'll probably have to scuff it up to some degree anyhow since the metallic will be dry.

      Lord how I know these questions might sound lame to experienced people but please keep in mind- only thing I painted was wood stuff and it's gotta be right or I watch it peel away as I drive it--- It may not look perfect but that's do to expeirence but with your help it'll be done correctly.

Edited August 29, 2020 by jeff53 (see edit history)

[F&J]

2 hours ago, jeff53 said:

" Is there a sanding method where I "won't mess up the metallic?"

 

 

 

as was said already, but in different wording;......... if you sand a metallic base coat (or metallic single stage), the actual "color" gets sanded off of "some" of the (silver colored) poly flakes.  This causes the color of the finished car to be lighter in spots where more sanding was done, and low spots like in orange peel depressions will be darker.  In other words, the overall car color will be blotchy looking and very noticeable.

 

When sanding only the clear, if you mistakenly sanded right through the clear coat, but just in certain spots, you will then end up with the same lighter blotchy look and putting more clear on will not fix it.  Meaning that if you sanded through the clear completely at raised edges, etc, you'd need to start completely over with new base color and then the clear.

 

For years it's been said that the clear must be done within the specifications time to have a permanent "chemically fused" bond of the clear coat to the base coat.  I would then  assume that if you do the clear coat weeks/months later, then the clear will delaminate from the base coat sometime in the future.

3 hours ago, jeff53 said:

"( since I'll probably have to scuff it up to some degree anyhow since the metallic will be dry."

 

Just to warn again; you cannot sand or "scuff" the metallic basecoat without causing the color to be affected. The darker the color, the more noticeable it will be.

 

Since you asked about details: There are two ways that a new top coat properly bonds to the previous paint layer.  One is by scuffing or wet sanding an old paint layer on a simple car repaint job.  That is a "physical bond" where the new paint hooks to the microscopic scratches in the older layer.   The base/clear system is not like that at all; it is a ''chemical bond", meaning the clear "mixes" or "melts" into the base coat.  It is not a physical bond.  If you wait far too long with the clear coat, then the clear cannot melt into the base. 

 

I hope you can understand what I've tried to explain in simpler backyard terms on how paint layers attach to another layer.

[jeff53]

40 minutes ago, F&J said:

 

 

 

as was said already, but in different wording;......... if you sand a metallic base coat (or metallic single stage), the actual "color" gets sanded off of "some" of the (silver colored) poly flakes.  This causes the color of the finished car to be lighter in spots where more sanding was done, and low spots like in orange peel depressions will be darker.  In other words, the overall car color will be blotchy looking and very noticeable.

 

When sanding only the clear, if you mistakenly sanded right through the clear coat, but just in certain spots, you will then end up with the same lighter blotchy look and putting more clear on will not fix it.  Meaning that if you sanded through the clear completely at raised edges, etc, you'd need to start completely over with new base color and then the clear.

 

For years it's been said that the clear must be done within the specifications time to have a permanent "chemically fused" bond of the clear coat to the base coat.  I would then  assume that if you do the clear coat weeks/months later, then the clear will delaminate from the base coat sometime in the future.

 

Just to warn again; you cannot sand or "scuff" the metallic basecoat without causing the color to be affected. The darker the color, the more noticeable it will be.

 

Since you asked about details: There are two ways that a new top coat properly bonds to the previous paint layer.  One is by scuffing or wet sanding an old paint layer on a simple car repaint job.  That is a "physical bond" where the new paint hooks to the microscopic scratches in the older layer.   The base/clear system is not like that at all; it is a ''chemical bond", meaning the clear "mixes" or "melts" into the base coat.  It is not a physical bond.  If you wait far too long with the clear coat, then the clear cannot melt into the base. 

 

I hope you can understand what I've tried to explain in simpler backyard terms on how paint layers attach to another layer.

 I did  and will heed the recommendations -you guys know your stuff and just as when I trained guys to drive semi- sometimes there just isn't another option when backing up a 65-70'- large car.
           Not to Sand- as I stated, I was just wondering if there was another way to - put the "clear coat on-- outside of the flash time or dry time ( that's why I listed the spec times)...

The "clear coat isn't on yet.... I plan on putting on 1 more coat, but just couldn't find the time to do it all at once anytime soon.

          I know there are some paints that " do not need" a clear coat--- that why the question... I kind of like the Matte finish and just thought -- what the heck maybe I can forego the clear coat all together.... I hear even some pros have trouble putting on clear coats.. So I know I'll have trouble.

          I also thought maybe just buffing and polishing it would be okay. Doesn't clearcoat,take a special spray gun? By the way thanks for getting into the tech part, ie there's a good reason for coming to you guys--- There's  more to backing a semi, than hop in,check your mirrors and start backing. Again thanks

[F&J]

51 minutes ago, jeff53 said:

"I was just wondering if there was another way to - put the "clear coat on-- outside of the flash time or dry time ( that's why I listed the spec times)..."

I don't think so, as far as guaranteeing the clear coat won't peel later.  I'm a bit lost on why you can't do the clear on the first color parts of your two tone paintjob.  You will already have it masked/taped, and it's just like adding another coat of paint just as if it was a single stage job instead. 

 

One important thing you might not know about spraying the base color for the first time:   It is not supposed to be thick layers of color like you would do if it was single stage paint.  Done properly, It will seem like a very thin layer of color, almost too thin for somebody that only used different paints/varnishes on furniture or farm equipment before.  The base color should not be very thick, it only needs to be consistent color and complete coverage of the primers that you don't want to show through the base color.   You get the thickness and protection from the clear coats only.  On a single stage paintjob, the protection comes from the thicker layers of color.   I mention this as I've seen people try to lay down their first base coat job in the same way they did single stage jobs, and you will use way too much base paint and not be gaining anything.

 

Others here could give you better advice on spray nozzle sizes because I only do single stage urethanes now, which in my opinion, can allow a backyarder to get a awesome finish easier than the former acrylic enamel paints.  It sprays really nice and I don't seem to have to fight with not getting dry spots or sags like I always did with A/E. ...and better yet, I never need to color sand or buff.  That's good because I'm not skilled enough with a buffer.

 

... And the last job I used a cheapie no-name siphon feed spraygun that a friend got as a door prize at car show.  It sprays single stage urethane as good as a high volume paint shop can do, and I doubt it cost $25.   The best advice on avoiding dry/wet spots is to have great lighting, that's why spray booths have lights from floor level to the ceiling, so the painter can see the reflections in the finish at every point on any panel.

[jeff53]

Well 1st part I guess I did right by accident--- I laid down what I thought was too thin of layers of the basecoat. Putting on the clear coat, all I was trying to do was skip changing over and then back to base to do the bottom then back to clear again. and my wife and I kind of I liked the "matte" color and I thought "well if she's happy I'm happy and maybe I can just forget the clearcoat. Guess not huh... I read all the scary stories about how hard it is to lay down, and how easy it is to get runs. I never would have even considered metallic paint -- if I knew I was going to end up doing the beast. Problem I seem to be having now with this last layer is--- not being tall enough to get the top of the car "evenly" I use a small step ladder ( 2 stepper) but doesn't give me the best reach ( as I noticed) I'm getting what I would call heavy and light streaks- didn't really want to try a 6' ladder- figure that's just asking for trouble. and as a past freelance photographer--- I know lighting is everything and lighting in my garage is only fit for critters like me -- but not for painting a car without several "do-over areas". Oh I have 4 shop lights on those tripods- but they are still pretty bad.Can't paint outside ( neighborhood issues) I would consider myself a backyarder---except this is the one and only time I ever paint a car and I'm only doing this- because after trying to get others to paint it since 2017 ( and losing money in the process) I figured if I didn't do it -- it would never get done in my lifetime... So I had a choice-- either sit and watch it rot before my eyes or take over and at least try to get it painted and back together... I so much wanted someone else to do this. Makes me puke just to think of all the leftover stuff I either have to throw out or find a spot for... My poor wife has never ridden in it and bless her heart-- she's been pretty patient with me saying " Sorry but we can't park your car in the garage until this thing is at least finished being painted

    Again thanks to all

[nickelroadster]

Getting light and heavy streaks means that you are not putting the paint on evenly.  If you are getting these streaks in the base coat, you are probably putting it on too thick and are not overlapping the coats.  You need to keep the gun moving and always pointed perpindiculer to what is being painted.  Have you got any instruction on how to paint?  The more light you have , the better.  I have often times used a light to hold in my left hand to use shadows will help you judge how your application is going.  I know the paint is expensive, but you probably need to practice some more to get a usable job.  I will assume that you will get runs in the clear coat.  These can be sanded out and buffed if you only get a few.  I would recommend that you get some instruction books or videos  from Eastwood or T.P. Tools instead of just trying to reason your way through things.  Do you not know anyone who knows something about painting? 

[jeff53]

Thanks and I've seen and read a ton of them, even dug out one from 1981 ( back then I wanted to do this-- work and life just got in the way as they say). Most painting books and videos don't really go into detail- just the standard and  normal stuff-- How to clean the gun/ how to get the football pattern/ angle - what orange peel and mottling and other spray look like and they all show how to do it on a vertical surface or something lying on a table. The perpendicular part for the roof is the hard part, I've been using a small 2 step step ladder- but I guess I'll need a little higher platform. I was trying to avoid making one--- ( safety reason) but I guess I'm gonna have to make one.Everything else looks pretty decent. Glad to know about the clearcoat . so I won't fret to much if I get some runs....

   I have an Eastwood Cat. but thanks for the other.  Only person I know that's willing to give out info is the at the  auto paint supplier and good thing I checked here before putting on mu clear coat- because they said to " wet sand " the base coat and then put the clear on and wet sand that also. ( wet sand in between base and clear). 

     Personally- I just wish this didn't need a clear coat at all.... but this is what the 2nd auto painter started with- so I guess I have to see it thru.

         2 curious questions- When watching the shows like Kindig and others- they seem to have guys covering the "whole body" in filler type stuff- I thought filler was just for small areas or it would crack. 2nd question--- All painting videos seem to show almost a cloud like foggy mist..... I can get the football shaped pattern okay and a fine somewhat okay mist- the tip is a 1.4 - but I can never seem to get the very fine mist.... My way seems to use a lot of paint..... But I'm not getting any fisheyes or orange peel ( the books and videos point out the gun settings but never really an optimal starting point.... Kind of like me telling a new driver - just stick it in gear and and start down a 7-9% grade.

     

[TAKerry]

The amount of air pressure and has a lot to do with the pattern, and the amount of mist and heaviness. You may have to play with that a little bit. I have a couple of benches from HD that I use all of the time. They are much easier than moving a step ladder around, and they are pretty cheap.

There is a 'flat' clear coat if you like that look. Thats what I painted my bike with:

[url=https://flic.kr/p/JqJByj][img]https://live.staticflickr.com/982/27846894478_966408cb12.jpg[/img][/url][url=https://flic.kr/p/JqJByj]2018-04-26_08-53-44[/url] by [url=https://www.flickr.com/photos/156399515@N07/]Kerry Grubb[/url], on Flickr

[jeff53]

Thanks, I was just trying to avoid clearcoat altogether. I was going to use or buy a bench but figured it wouldn't be any higher than the 2 step/step ladder I have. My friggin problem is the big guy figured I needed bigger arms not a set of longer legs or a longer reach. Oh by the way guys, just in case you're wondering-- You guys steered me correctly- per the factory techs. at Omni. I finally got a hold of them also- ( been trying for a while)and just as you guys said--- put on the base coat then put on the clear coat--THEN wet sand and stuff. So I'm gonna give my paint supplier the benefit or the doubt and say I had to of heard him wrong, however the factory tech. couldn't figure out why they gave me Omni MBC for the top and Omni MBP-Plus for the bottom--- even tho I had a can from the pro of Omni MBP with me. He did say they will be okay together. So thanks again and if everything runs correctly- hopefully the complete paint job part will be done by the end of next week--- whew!! When this is done I should have arms like a great ape- a ton of sanding and re-sanding for a greenhorn.

Edited August 31, 2020 by jeff53 (see edit history)

[nickelroadster]

What I meant when I said you will probably get runs is that a few of them can be dealt with .  I did not mean that you could get curtains of them.  Practice, practice.  Even if it cost you a little bit.  Work on getting a very steady stroke with even coverage.  The first car I painted in a garage when I was seventeen.  It didn't turn out too bad.  It had as solid blue color and I did have experience painting model cars (which did educate me on spraying principals.  I think tha tmost of us would like to see you come up with a paint job that will work for you.