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67Elcamino 07-06-2012 11:23 PM

Sanding before cutting and buffing
 
Im using SPI universal clear and following 'the perfect paint job' instructions from the manufacturer.

After letting the final clear coat sit for 3 days Im sanding with 800, 1000, 1200, and finishing with 1500 before cutting with a wool pad and polishing. I have read other posts where people go up to 2000 on wetsanding. Is there a huge difference between 1500 and 2000 if Im going to cut and buff thereafter?

Also, I read the instructions and it recommends cutting and buffing within 2 days to 2 weeks what happens if its been a month or more?

Jallopy 07-07-2012 01:25 AM

There is probably no difference if you stop at 1500 ...It may take you slightly longer to remove the 1500 scratches with the buff .
The wool pads are quite agressive compared to the foam pads so it should cut back quite quickly.
If you are just learning with a buff I would recommend a foam pad

The longer you leave it to sand and buff the harder the paint becomes as it cures.

A lot of people will re sand and buff their car again after a year or longer and have a perfect finish, so dont worry if you cant get to finish it within a couple of weeks.

deadbodyman 07-07-2012 08:17 AM

sanding with 800 ,1000 makes me cringe and for the life of me I dont know why Barry recomends doing this but since your following his instructions ,follow them to a tee...even use the compounds he recomends maybe he knows something I dont about cutting and buffing,it wouldnt be the first time.
If you havent already started the sanding try doing it his way on one panel then on another panel start with 1200 then 1500 ,then on another panel just 1500 alone and see which way you prefer.
usually I start on the top surfaces but for you I would start on the sides (because they are easier) see which way works best for you, getting 800 scratches out of a hood might take a couple days alone even if its been taken up to 2000 .....
For those who might not understand why I would say all this,Think back when you did the filler work and sanded it down with 36 then went to 80 ,you couldnt sand all the deep 36 scratches out could you ....Sure the top smoothed out real nice but the 36 scrathes could still be seen so they needed filling with poly putty or building primer ,right? its the same thing with clear....I've never used 800 on clear and the only thing 1000 is good for is sanding out a run and even then you want to be careful not to sand the run completely out and down to the surface you'd want to leave a little of the run and finish it with 1200 and 1500...Those 1000 grit scratches are a bear to get out completely....
But like I said maybe I'm missing something so if anyone has done it this way starting with 800 how did it work for you and how long did it take????

John long 07-07-2012 08:45 AM

Mike brings up some good points here. I for one do use 800 to color sand. Just started that in the last year ot too. What I do is use an aluminum block under the 800 which levels the orange peel really well. Once I have the orange peel cut level I switch to a hard rubber block and go to 1000 or 1200. I find that the speed and efficiancy that it levels the orange peel makes up for the extra time to take out the sand scratches. It may be that a painter with a good booth, gun, and technique could shoot a slick enough paint job that he may not like the 800 but I find if I start with 1200 it takes sooooooo long to level the orange peel.

John L

Chevymon 07-07-2012 09:33 AM

Quote:

Originally Posted by deadbodyman (Post 1571585)
sanding with 800 ,1000 makes me cringe and for the life of me I dont know why Barry recomends doing this ????

The reason he recommends it is because his clears are high solids and when applying enough to color sand (3 or 4 coats) then you will have the urethane wave, and the only way to remove it is with hard block course paper. Keep in mind that the perfect paint job is for show cars, a lot of the procedures in it are very time consuming.

urethane wave/lump whatever you want to call it ?

67Elcamino 07-07-2012 10:17 AM

I started with 800 where there is visible orange peel and where theres minimal I started with 1000. I do see you point in the 800 creating scratches. Im going to do what you recommended and start one section with 800 and one with 1000. SPI didnt recommend starting with 800 but does mention to use up to 1500.

Chevymon 07-07-2012 11:32 AM

It just depends on your level of acceptance, what ever makes you happy is OK. Testing different procedures will tell you that. I know a highly experienced painter who only uses 1200 and then just buffs with one product, and can't understand why anyone would use more.

tech69 07-07-2012 02:58 PM

It's my opinion that if you aren't a master buffer then you have to respect the work and by that I mean if you're a newbie buffer don't go thinking you can put a 1000-1200 scratch into clear coat and not have issues...and I'm talking issues that fly in your face when you're compounding and/or polishing and THEN finding out you haven't cleared away your 1000-1200 scratches. Then you're walking backwards and we've all done that. This is why I am careful with what grit I put in that clear. I start with 1500 in a /\/\/\ type sanding pattern THEN I go with sanding with the direction of the bodylines (front of car to back) with the block cocked a little so the corner of the paper around my soft block doesn't gouge. It's much easier to cancel out a scratch going against the direction of the scratch and it will also tell you that you have canceled them out correctly by just looking at the direction of the scratches. Once I know all my scratches are going straight then I know all my scratches are 2000. At that point it's not so important to sand in another direction cause a 2000 scratch isn't troublesome. I then go to 2500 by hand or trizac 3000. It's simple and safe and in the end I don't have to backtrack from being ready to polish to then seeing something that makes me go back to wetsanding. It eliminates all that crap.

the only time I go to 1000 is when I deal with sags or runs. Even then I don't fully sand them out with 1000. I'm not a master buffer but I found this procedure makes it appear that I am. :)

John long 07-07-2012 08:09 PM

The sand scratches created by wet sanding with 800 are far more shallow than most orange peel. The only issue you have if you level the orange peel with a hard block and 800 or 1000 grit is making sure you do a quality follow up with 1200 and/or 1500. If you don't, you will instantly know it when you begin to buff. Yes, you will have to back up and sand those scratches out with 1500 but that is not the end of the world. The important thing that must be done for a first class job is leveling the orange peel, nibs, dust and trash. You can give attention to the dust spots, knats, and misc trash with a fine paper but to color sand orange peel out level starting with 1500 will take forever. I used to start with 1200 until I talked to a fellow who had just rubbed a car that had a finish "you could walk right in to". I asked him what his secret was and he told me he started out leveling it with the metal sanding block and 800. After trying it I was sold. Quality work takes time but is worth it in the end.

John L

deadbodyman 07-08-2012 08:01 AM

Quote:

Originally Posted by Chevymon (Post 1571601)
The reason he recommends it is because his clears are high solids and when applying enough to color sand (3 or 4 coats) then you will have the urethane wave, and the only way to remove it is with hard block course paper. Keep in mind that the perfect paint job is for show cars, a lot of the procedures in it are very time consuming.

urethane wave/lump whatever you want to call it ?

All I use is SPI clear I dont get a urathane wave at all That what happens when the clear cures unevenly and the main cause is applying too much clear all at once...If I'm going to apply more than two coats of clear I'll let the two coats cure for two days then sand with 600 and apply two more coats.I believe there are a couple more causes that when combined create the perfect storm of a urathane wave...first the amount of hardner has to be exactly the same for these two coats and the ONLY way to be sure is to mix the clear you'll need all at once ....and I truely believe spraying with too much pressure is another cause...Theres probably quite a few more but honestly I've never had a problem with the wave although I have seen it and one time while watching a painter I could actually see it happening (I think) while he was painting but the pressure he was using was way too high...
So I can see starting with 800 (kind of ,I guess) if you have the wave but If it was me and I had the wave I'd sand it (with a block and 600) and reclear it.....
I am glad to hear I'm not the only one that hard blocks the clear but I block with 600 and reshoot it rather than buff but thats only on my best work..
One thing I have learned in over 30 yrs of doing this work is theres no one way to do something and what works for me dont necessarily mean it'll work for everyone....But for me buffing really sucks and I hate it, but I still want that perfectly flat look I just dont want to get it from buffing.
INMO, the "perfect" paint job would need NO cutting OR buffing..LOL
but no matter how slick I spray my clear and think I only have to nib out a few pieces of trash ,once I start nibbing I ALWAYS end up seeing some peel and end up sanding edge to edge....
The main problem is everybody THINKS they want the perfect paint job when they paint thier 1980 suburu themselves when all they really want is a nice,respectable job they can be proud of...You ever notice most threads say whats the BEST way to fix this or whats the BEST primer or whatever and what they really want is whats the best way to repair or material to use for this "paticular" car and what your using it for...
I cant even tell you how many times someone will come to the shop wanting my best work and point to my old impala and say just like that one...well that impala was never cut & buffed and has trash all over it...but at 5' away it looks pretty darn good ,slicker than dog poop but just average at best. can you imagine how mad someone would be when they find out how much work it is sanding that 1980 suburu starting with 800....when all they really wanted was perfect for them...
Besides in 90% of the cases its not a urathane wave that is the culprit for a newbie or even a pro,, it's the bodywork wave and you can sand the clear all day long with 800 and you'll never get it out...kinda like polishing a turd...
Well, I've rambled on long enough I hope I've made a little sence and gave a few guys something to think about when the time comes to paint thier car...

Chevymon 07-08-2012 08:23 AM

Quote:

Originally Posted by deadbodyman (Post 1571832)
I've rambled on long enough I hope I've made a little sense ...

You made a lot of sense

deadbodyman 07-08-2012 08:48 AM

Lets give credit where credit is due, painters...the best paint jobs start with the best bodywork...and thats the begining and the end of it...So the next time someone says how nice your paint work is ,insted of just saying thanks and taking all the glory,how about telling them dont thank me ,thank the bodyman,it wouldnt have been possible without that fantastic bodywork....After all who you gonna blame if theres the slightest problem????

MARTINSR 07-08-2012 09:21 AM

"Made a lot of sense" is right! :thumbup:

This thread should be made a sticky, this thread has provided some GREAT information from everyone, if there is one thing that pops up over and over and is one of those frightening steps for a newbe it's cutting and buffing that paper thin layer of gold! The information gotten from this thread is VERY valuable information indeed!

I am with you Mike on the "urethane wave" too much being applied too soon is generally the culprit if you ask me.

First let me say that I LOVE cutting and polishing a show quality paint job, one that I shot of course, cutting and polishing someone else's work is scary to me even after all these years. But doing that final touch on a car, after a million and a half hours of welding and bare metal and blocking and all the hard work :sweat: you get to take your time and cut that micro thick film down to perfection and make it SHINE, I LOVE it!

And my real "color sanding" experience started nearly 35 years ago doing complete show quality lacquer paint jobs where they got fully color sanded after every five coats (for a total of 15 usually) and I am talking every single square inch, EVERY single spec of orange peel or texture, even in the jambs! Like I say, I LOVE this stuff!

Anyway, as Mike said there are many ways to do this and many will get the job done well. If you have five different guys there may be five different ways that will exist simply because of five different talents. We all have had different lessons that have taught us to go down a slightly different road to get to the same end result.

The one thing I have always done is try to apply a perfect layer of product (be it primer, paint or clear) in that I have the most consistent film thickness. Then when color sanding I sand it the same way, with the most consistent removal of film leaving the most consistent film in the end. Sounds pretty much common sense and that is what most of us do, but I can't emphasize enough how important it is to cut evenly.

The coarser the paper, the faster this can get out of control, so walk softly when using the 800. And remember when I started doing this we didn't even have the 800! We did it with 600 and when that "ultra fine" (the first paper finer than 600) came out it was a GOD SENT!

Ok, my method in a nut shell. I don't remove ALL the texture with the first paper (typically 1200, depending on what it needs, some times 1000 or even that 800 in areas). This is one of the mistakes I feel guys will make. They cut it perfectly flat and then move on to the next grit, in my opinion that is removing too much material, and unnecessarily I might add. If you are going to have to be sanding out sand scratches from the 800, removing material, why on earth would you need to cut the texture completely off with the 800? Why not cut it down to where you have learned the next step (being 1000) is going to cut the texture anyway when cutting down thru the 800 scratches?

So basically I cut the texture down to where the next grit is going to remove the previous grit and the remaining texture, this is at least for the first couple of steps 1000-1200 but maybe even going to the next, 1500. Then leaving zero texture for the 2000. With this method you are removing the minimum of that paper thin film of gold. :mwink:

I make sure that the panel is PERFECTLY clean before each step. The bucket is PERFECTLY CLEAN. We are talking clean enough to drink out of, and I am not exaggerating, clean enough to drink out of. The paper is again, perfectly clean. If a piece ever falls on the ground it is NOT reused without a trip to the faucet or sink to wash and get a very close inspection. Any rag to wipe the surface is kept clean like I was using it to wash my face. If the rag were to drop on the floor it would NOT be reused no matter what, a replacement is gotten. We are talking operation room clean here, there is nothing like picking up some microscopic piece of trash under the 2000 grit paper requiring you to cut that layer of gold more! :pain: So keeping things clean is of the UPMOST importance.

And on products, I use Mequiars products Click here

I have not used any paper that even comes close to the "Unigrit" paper they sell, it blows away 3m by leaps and bounds. The "Power cleaner" compound is the best I have found. click here It doesn't take nearly as much as other brands which means you don't have your walls and the rest of the car covered in splatter. It is amazing stuff if you ask me.

But honestly, I have said for years if Mequiars starts making televisions or opens a restaurant I will be there, they are THAT good of a company.


Brian

tech69 07-08-2012 10:56 AM

cleanliness and being anal is super important in paint and cutting and rubbing. It's the difference between a few swirls and a lot. We hired this guy for about 3 months, 30 years exp, had a car on a cover of hot rod and even an article on the build, but dropped the ball big time. Bodyman/painter but was sloppy, which was the reason he was later fired. He hopped on a few cars with us but mainly did the low end spot jobs. Then one day a fully restored Camaro they had only painted and changed the color of the stripes previously, had come in for some spot repairs around the drip rails...First he put a DA pigtail on the driver's glass, scratched the windshield with his moulding tool, and may have also cracked the windshield in an area where he had trouble getting the moulding off(he denied it) the tiny spot repair he did that got poly primed needed to be primed twice.:nono: So he does a decent job spraying it but now it's time for buffing. This is where the excuses came... He just couldn't get the swirls out, burned through one area, and lost his job for how he reacted to it and his lack of attention. Too stubborn to listen. In a nutshell, we all would go back there to check his "progress" and without knowing too much of his techniques I have an opinion on what killed the job...NOT KEEPING THE CAR CLEAN and not being thorough.

He didn't have a surefire way to get rid of 1000 scratch marks, which tells us he used to work in a crappy resto shop but let's not forget the time buffing and even polishing before his left over 1000 scratches were pointed out. At this point he's buffing and rebuffing trying to fight swirls while we occasionally and quietly would go over to the car to eyeball the areas where we saw sand scratches, and this guys trying to go to polish while we're still seeing swirls AND sand scratches. So then the excuses come out about product, waiting to long to cut it open, etc-etc. The car full of wool, dry compound(even in the cowl vent), break thrus on a few corners, mega swirls, and a disgusted boss. It got repainted and completed by somebody else. The moral of the story, this guy had a few guys fooled about his ability and it was cutting and buffing (out of all things) that finally showed everybody he over sold him self in the interview process by embellishing his skill level. So I have that as a reminder as to why I wouldn't recommend a non professional to cut a clear open with 800. A non professional painter might leave a lot of orange peel and starting with 800 makes me cringe at the thought of how much will be left to protect the car when it's all said and done. I don't think I've had to deal with urethane wave. I think if the bodywork and prep is perfect than the car will look perfect, and with that said I wouldn't recommend a newb to cut urethane waves out cause most likely the car won't be perfect anyways. It's just adding a bunch of risk to the equation and not yielding a noticeable result for their skill level. Not knocking anyone who does this technique, just don't think it should be recommended without a warning about implications.

67Elcamino 07-08-2012 10:58 AM

2 Attachment(s)
Brian, Im with you. This is my first car I have painted. I just learned a bit of welding, hammer and dolly work, priming, blocking, sealing, painting, clearcoating and now cutting and buffing. Its been a year and a half but thanks to you all and all of the advise. I couldnt of done it without this site.
That said I do not want to cut too many corners after all that hard work. I came to the conclusion given that I didnt lay the clear that smooth and have some trash in it that Im going to cut with 1000, 1200, 1500 then buff with wool pad and polish with foam. Even though its taking me a bit longer to cut the orange peel with 1000 its keeping me from cutting through the clear in some corners and in the long run saving me some time.
I feel like I will paint my next car a lot better from what Ive learned with this car. I plan on selling this car as soon as I finish because I have two more projects behind it that Im planning on keeping (1940 desoto coupe, and 1964 Cadillac deville)


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