Wetsanding and buffing fresh paint

[transamfan]

I think I`ve decided to go ahead and start with 1000 on a block to get all the orange peel out and use the DA from there to refine the scratches. I know that in the past I have had ripples in panels that looked flat before the cutting and buffing were done, and I`ve always felt that they were do to an uneven clear coat surface created from the DA. I`m gonna give the block a try and see how it works out. I think we can all agree that after using 1000 grit on a block to remove the orange peel I will have a uniformly flat surface of clear coat to polish up.



Another thing that has not been mentioned yet in the discussion is urethane wave. This is something that us painters have to be aware of in addition to orange peel when layering clear on heavy for custom jobs and show cars. This is why a lot of times painters will spray 3-4 coats of clear, block it down with 400-600 grit, and then spray a final flow coat. I suppose that if you were to put the clear on too heavy in the flow coat you could end up with some wave as well which would require sanding with a block to get it out. I really doubt a DA would flatten urethane wave.





One of my questions that still hasn`t been addressed really is this...When compounding and polishing until all defects are removed from the paint, is it possible for the final appearance to be different if a different set of products were used? Is the final appearance dependent only on a perfectly flat, smooth, and defect free clear coat, no matter if I got there using Menzerna, Meguiars, or any other compounds/polishes? Since I use the same clear on every job I do I am looking to find the magic formula for cutting and buffing that I know will produce the best results every time. Unlike in the detailing world, once I figure out what works best on my clear I will be able to use the same process every time.

[C. Charles Hahn]

Again, flat body work is on a totally different level than the flat outer surface. Mainly because your base(primer) is finished in much coarser abrasives. Especially seeing that clear coat is typically the thickness of a single sheet of paper. External waviness comes from incorrect removal of the surface (i.e. orange peel). As long as that has been done, I really don`t believe anyone`s eye can pick up a variance measured in single digit microns. It goes beyond passion at that point. In most extreme cases, to create a "perfect" finish, besides removal of orange peel, the base requires extensive blocking in between coats too. Now that`s a noticeable difference.

:werd: to the :nerd:

[C. Charles Hahn]

One of my questions that still hasn`t been addressed really is this...When compounding and polishing until all defects are removed from the paint, is it possible for the final appearance to be different if a different set of products were used? Is the final appearance dependent only on a perfectly flat, smooth, and defect free clear coat, no matter if I got there using Menzerna, Meguiars, or any other compounds/polishes?

In a word, yes. It really depends on how your particular paint reacts when worked with the abrasive set in a given polish or line of polishes. The best thing you can do is give some other finishing methods a try (as mentioned before 85RD should finish down better than 106FA because it`s a finer grade polish, or you could give M105/M205 a shot, or 3M PI3000 to finish with Ultrafina SE, etc.).



The "jeweling" effect from different techniques and different pads/polishes can most certainly make a difference in the final appearance and in large part it`s the pad/polish/speed/pressure coupled with whatever meshes with your particular environmental conditions and buffing style.

Since I use the same clear on every job I do I am looking to find the magic formula for cutting and buffing that I know will produce the best results every time. Unlike in the detailing world, once I figure out what works best on my clear I will be able to use the same process every time.

The only thing I would say to that is to keep in mind you`ll want to account for any variances in the application and curing environment.



If you have a booth that is perfectly controlled for temperature, humidity, airflow, etc. and always shoot under the exact same conditions, you`re right that the paint should react the same every time. However if you`re shooting in conditions where one of those variables changes, the paint could cure differently and thus react uniquely as compared to a previous spray-out.

[transamfan]

That`s what I thought. The last car I did was black and it came out nice after polishing but I felt it could look better. I`m gonna get some 85RD and give that a try and I suppose I`ll just spend a lot of time doing some comparisons on this next one.



When it comes to variations in painting conditions, they`re all over the place. It`s nearly impossible to spray in the same conditions no matter what you do. While I`m sure it will make a difference, I think the differences in how the clear finishes out would be minimal compared to the differences you guys deal with when working on all the different cured factory paints.

[Ron Ketcham]

David, in my opinion you covered one of the "keys" to obtaining the correct finish.

One thing in these discussions that should be mentioned is "what manufacturers clear is used and which one of them".

Many clears out there and each has it`s own quirks.

Another thing is "how long was the clear allowed to air cure", since the ones referred to and used by folks here require air and time for crosslinking.

One other variable is if the clear requires a catalist and was the correct percentage added.

When I hear the term "soft clear" regarding refinish material clearcoats, and do some investigation, find one or both of these items to be the reason for the softness.

In most cases when one attempt to wetsand and buff "soft clears" there may be some "movement" of the substrate resulting in "waviness".

Just a thought or two.

[C. Charles Hahn]

In most cases when one attempt to wetsand and buff "soft clears" there may be some "movement" of the substrate resulting in "waviness".

By movement of the substrate, I assume you mean panel flex due to excessive downward pressure applied by the operator during the sanding and buffing procedure?

[David Fermani]

David, in my opinion you covered one of the "keys" to obtaining the correct finish.

One thing in these discussions that should be mentioned is "what manufacturers clear is used and which one of them".

Many clears out there and each has it`s own quirks.

Another thing is "how long was the clear allowed to air cure", since the ones referred to and used by folks here require air and time for crosslinking.

One other variable is if the clear requires a catalist and was the correct percentage added.

When I hear the term "soft clear" regarding refinish material clearcoats, and do some investigation, find one or both of these items to be the reason for the softness.

In most cases when one attempt to wetsand and buff "soft clears" there may be some "movement" of the substrate resulting in "waviness".

Just a thought or two.

Hi Ron. Glad you got my PM and thanks for your input. I totally understand the different quirks/characterists among the refinish manufacturers and their lines. Some good...and some not so good.

By movement of the substrate, I assume you mean panel flex due to excessive downward pressure applied by the operator during the sanding and buffing procedure?

Not sure if the substrate he`s referring to is the panel(metal) or the base(color) or primer. He is referring to soft clears so if that`s the case you can actually create waviness in your clear from buffing too? Can I get some more feedback on this Ron?

[Accumulator]

I think I`ve decided to go ahead and start with 1000 on a block to get all the orange peel out and use the DA from there to refine the scratches....

I`d much rather do the final sanding with something *MUCH* milder if using a DA to remove the sanding scratches. 4K is a piece of cake; 3K is easy enough; 2K starts to get a little demanding but is perfectly doable; coarser than that...well...I`d rather not do it that way, but that`s just me.

[JohnKleven]

You can also create waviness in the clearcoat by using a D.A. for sanding. When going back and forth in the same area, you can create low spots on the end of the stroke. Similar to painting something, if you have are spraying and going back and forth without turning the paint off at the end of each stroke you can get runs on both ends, and looks something like this. |------| when painting. Using a block will prevent this from happening.





John

[Ron Ketcham]

By "Substrate", I am referring to the total paint film build it`s self. Wether the acid etch primer, surface primer, base coat or single stage, clear, all have different curing times, and while may appear to be "dry or cured", may not actually be.

This may create the condition I was referring to.

[RaskyR1]

Nope. A d.a. Is NOT as flat as blocking, especially if you`re using an intermediate pad onyour d.a. I do probably 10+ full car sands per year, some I do dry with d.a. Som

wet with a block. The D.A. Cuts the time dramatically, but will never finish as flat. You won`t find a d.a. Being used on big money hot rods.



I like to go from 1500-2000 as it makes for an easier polish in my opinion.





John

I`d have to agree with John on the long block sanding doing a better job than a DA at leveling off the paint. It takes a lot more time and may not be suitable for all panels shapes, but when time is not an issue and I want the paint to be as flat as can be, I will use a block by hand as much as possible.



I do like to finish it off with the DA though and on most my jobs I`ll just reach for the DA.





Trying out the Mirka Abranet Soft right now....me likey! Thanks BuffDaddy!

[Barry Theal]

Rasky I have been through alot of different sanding abrasives in the last few months. First trizact and then norton and now I`m on the Mirka set up as well and love it! Great for DA use. I`m with you for sure on the block sanding by handing though.

[David Fermani]

You can also create waviness in the clearcoat by using a D.A. for sanding. When going back and forth in the same area, you can create low spots on the end of the stroke. Similar to painting something, if you have are spraying and going back and forth without turning the paint off at the end of each stroke you can get runs on both ends, and looks something like this. |------| when painting. Using a block will prevent this from happening.



John

Waviness? Maybe a variance in orange peel/flatness, but I don`t see how you can create waviness in clear from a using DA? We`re talking a difference in thinkness of probably less than 5 microns. Something this minute can`t even be detected with your eye. OTOH, when doing body work, yes. Most painters hand sand. Even usually on blend panels, but we`re talking thicknesses that are visable.

[Kevin Brown]

Now we`re talking.... THIS is an autopia thread!!!



Leveling in the sanding world means to minimize variances in the high and low spots of the sanded surface. The more level the surface, the more accurate a reflection will be. This is easy to see in a typical swimming pool. If there`s nothing disturbing the water, then the reflection will be pretty accurate. If the wind kicks up or someone is in the pool splashing about, the reflection is not as accurate.



I think this is understood by most folks. Orange peel removal isn`t what we`re discussing, but rather, creating a consistently leveled surface across a long range or large area is the goal.



I agree that hard blocks, or long blocks, typically excel for leveling.

There are specific and logical reasons for this.



In theory we could replicate similar results using a random orbital sander, but man, you`d have to be really good with a machine to do it. Plus, you`d have to be open to the idea of making a customized backing plate and interface pad.



Let`s get to the fun stuff, and cover some basics for the guys that are somewhat new to this.



A sanding block or backing plate that is hard can also be flexible.



Materials such as balsa wood, plexiglass, glass, steel, and aluminum are hard. I have personally used, seen other guys use, or heard of other guys using these materials to make sanding pads.



Poke any of these materials with a sharpened pencil and the lead will break with ease, leaving the materials unaffected, or only marginally affected. This assumes there is enough thickness to withstand the assault, and most sanding blocks or backing plates are thick enough.



If the material is thin, it has the potential to flex, bend, or twist.

With the exception of glass, I think most of the listed materials will bend or twist with relative ease. As an example and to give you a visual, a typical metal ruler can bend or twist, yet handle the onslaught of a poke from a pencil lead. In fact, if you wrapped a sheet of sanding paper around a flexible metal ruler, you`d have the makings of a simple yet effective sanding block!



If we decided to use a thin steel ruler as a sanding block, we certainly could. Ideally, we would glue a long foam block onto the back of the ruler, and use the block as a handle or gripping area. For the sake of discussion, let`s continue on with this idea.



We could use PSA (peel and stick adhesive) sanding sheets, or cut an appropriate length of sandpaper from a sanding roll and attach it to the ruler. I personally haven`t seen too many varieties of paper at the higher grades we are discussing, so we must improvise.



We could use a thin coating of spray glue to attach sandpaper sheets to the ruler, or attach lengths of paper via duct tape, and glue that to the ruler. Of course, the paper should be trimmed to the width of the ruler, and it would be critical that the individual sheets of paper be positioned to tight tolerances in relation to each other- no overhang, no large gaps.



Note: readily available long blocks feature clamping systems that allows us to attach lengths of sandpaper to the block at each end. Other blocks are hook and loop compatible, while still others are smooth faced to easily accept PSA style papers.



Once we found the best way to mount the paper to our ruler, we could use any length ruler as a hard but flexible sanding block. 12", 18", 24", 36", and even 48" rulers are readily available.



By using the longest ruler that would work on our sanding project, we could affect a whole lot of peaks at once, and level them to the same overall height. These areas, when polished, would reflect in tandem. Even if we didn`t completely remove all of the orange peel, we would still see a more accurate reflection across the surface.



A sanding block or backing plate that is soft will more readily contour to the nuances of a surface.



If we took our ruler block and mounted a thin piece of foam to the sanding side of the ruler and then attached the sandpaper the foam, it`s almost guaranteed that we would not be able to level the surface to the same degree as a ruler without the foam.



But, if we wish to make our sanding job easier to accomplish... or if we`re working on panels that do not allow us to use ruler-length sanding blocks... or if we would rather not create a laser-level surface... or if the surface needed sanding only to remove very fine texturing and dirt nibs (including dirt in the lower lying levels of an orange peeled texture), then we would probably be happier using a sanding block featuring resiliency, squishiness, and conformability.



This is why most hand sanding blocks are short and soft.

Human hands aren`t all that long either, so there`s a bit of logic behind the sizing.



With all this being said: Could a DA machine outfitted with a sanding disc level as well as hand sanding?



Certainly, but only as good as an equal length hand block, and the block would have to feature the same characteristics (hardness, stiffness, cushioning, etc.)



In other words, if we are sanding with a 6" diameter disc and using a machine featuring a 5/16" stroke, then our sanding disc will effectively level an area measuring 6-5/16" in diameter. This assumes we don`t move the machine at all, but instead hold it in place as it runs.



If we removed the disc from the backing plate and placed it onto a hand sanding pad made of the same material as the backing plate, and then moved the hand pad no more than 5/16" in a back and forth pattern that mimicked the movement made by a DA sander, we would create a very similar sanding result.



But, if we happened to be using a backing plate or hand pad that offered cushioning, resiliency, or contourability, the machine would likely offer up a bit more leveling ability.



Simply put, if the machine moved the sanding disc at a higher rate of speed than your hand could, there would be less time available for the pad to adjust its position in relation to the paint surface. To more easily understand this, imagine driving over a very bumpy road at 5 MPH, and then again at 50 MPH. There`s simply not as much time for the suspension to react to the bumps, so the tires would likely not be as well planted as you traveled across the bumps.



Oh man, this is a lot to write in a hurry... I hope it is making sense so far.

I`m gonna go ahead post this, then add some diagrams on the next post.

[Kevin Brown]

O-kay.



Some diagrams that may help, and more discussion.

This one compares a long block to a short and long stroke sander.

If you want to see a clearer shot of it, I have a pdf version on my site:



Machine Stroke- How It Affects Sanding and Polishing Performance



The diagram is on page 9.

I don`t usually link it because it is a site that sells stuff.

MODS- if I am not supposed to put a link, feel free to remove it.



The type of backing material a sheet or disc features can also affect leveling.



To be clear, the backing is the piece of material that the sanding media is attached to.



Several types of backing materials are used to make backings for discs, and the type of material is a BIG deal in terms of how the disc performs.



In general... if we have two discs featuring identical backings, except one has a backing that is thicker than the other, and we are using a backing plate that is soft and cushiony:



The disc with the thinner backing will level to a lower degree, but contour to a higher degree.

The disc with the thicker backing will level to a higher degree, but contour to a lesser degree.



The harder the backing plate, the less of an issue backing thickness becomes.



Now, here`s where things get a bit tricky.

Some discs feature a piece of foam placed between the backing material and the attachment material. Most times, the foam increases contourability at the expense of leveling ability. But really, the characteristics of the sanding disc`s backing determines how much an effect the foam has on sanding.



Super thick and stiff backing?

The disc may flex well, and follow curves and complex panel shapes, but it may not contour to every nuance of the surface, such as orange peel.



Super thin and pliable backing?

The disc may follow every nuance of the surface and follow curves and complex panel shapes, but may not level the paint surface.



What if machine speed is maximized?

The effects of foam may be minimized.



Check out these discs featuring foam:



Mirka Abralon:

Tremendous contouring ability, wide range of grades. These are a kick to use, can be used at high or low speed. for me, low speed is better because the sanding pattern is smooth, and the abrasive particles stay attached to the disc longer. Higher speed offer a tiny bit more leveling, and can keep the disc cleaner, as rotational forces fling debris from the disc more readily than slow speeds.

Magnified shot:

Mirka Abranet Soft:

Excellent contouring ability at low speed, fantastic leveling ability at high speed. Compared to discs that use paper or film backings, the net material allows water to pass through (like treads on a tire. So, you can sand with water, use higher speed if desired, yet hydroplaning is not an issue.

Magnified shots:

Meguiar`s Unigrit 3000 Foam Finishing Disc:

Unmatched finishing capability... it`s like having thousands of super soft abrasive squeegees gliding across the paint! Virtually no ability to level, but at this point, you should be refining the surface to shorten buffing time rather than worrying about additional leveling.

Some diagrams comparing film, net, and cloth backed discs. These are also on my site, and are clickable.



When should Abralon be your first choice?



All about Mirka`s Net Mesh technology.

About film or paper backed discs:

Film or paper backed discs generally feature maximum leveling potential, but when used with water, they tend to float or hydroplane rather easily. This leads to inconsistent sanding results, as some areas may be sanded perfectly while others are barely affected by the sanding disc. Once the water is displaced, the disc, oftentimes spinning at a rapid clip (due to a lack of frictional resistance) makes a crash landing atop the paint surface. This leads to pig-tailing, gouging, or scouring.



I hope this info didn`t miss the mark, or stray too far from it.

I find this all to be so interesting, and there are lots of things to consider.



The biggest thing that limits our ability to use hard-backed backing plates has to do with user technique. If while sanding we happen to tilt the machine even slightly off kilter, the edge of the disc can dig into the paint. This can create some pretty dastardly sanding marks, especially if we`re using coarse grades of discs. That`s why most backing plates made for sanding discs tend to be soft and pliable.



Now... think you`re pretty good at handling a machine?

Why not make your own backing plate/interface pad combo?



Get a stiff backing plate, and attach a foam interface pad to it. Then, get ahold of a piece of Plexiglas, cut it to the size of the disc, and attach Velcro® hook material to both sides. Slap on your disc of choice, and get to sanding!



The foam interface would help to minimize user-applied tilt variances, so if you happened to get the machine a bit off kilter, the interface would compensate for it. This setup would be ideal for flat panels, but terrible for curved or complex shaped panels.



That`s all I`ve got! For now...