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  1. #1
    Mike Phillips
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    Two Schools of Thought - Sanding in Straight-lines or in a Crosshatch Pattern

    Two Schools of Thought when Hand Sanding - Straight-lines or Crosshatch Pattern

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    There's two schools of thought on the correct method or best method on which direction to move your hand and backing pad when hand-sanding.


    Straight-line School of Thought
    This method means to to sand in only one direction with all sanding steps. The perceived benefit is it will keep all your sanding marks in the same direction. Then, if you want to take this thought deeper this would mean if you don't get all your sanding marks out of the paint then at least they're all running in the same direction and my guess is most people will think this won't look as bad as sanding marks left in the paint that are in a crosshatch pattern and to some level straight-line scratches might be less noticeable and less unsightly than crosshatch scratches.


    Crosshatch School of Thought
    This method means that with each change in grit size of sanding or finishing papers, you sand in a different direction 90 degrees away from the previous direction. The goal is as you move to a higher grit paper you completely sand-out all the previous sanding marks that were running in the 90 degree angle opposite from the direction you're sanding with in subsequent steps.

    Now assuming you sand all the previous sanding marks out you would then only be left with sanding marks running in one direction. If you don't remove all the sanding marks from previous sanding steps you'll have a crosshatch pattern of sanding scratches in the paint of varying depths. At this point you can either re-sand and try to remove the 90 degree sanding marks or move on to the compounding step and try to remove all the sanding marks with a rotary buffer. If you don't remove all the sanding marks using a rotary buffer then you'll be left with a crosshatch pattern of sanding marks in the paint and these will tend to be easier to see than sanding marks all running in one direction.



    Sanding in Circles
    Don't sand in circles. Circular motions work great for spreading out of coat of wax over a painted panel but don't work well for sanding on car paint. One reason for this is because the idea behind sanding paint in the first place is to remove some type of defect, a lot of times this will be orange peel or some type of damage that caused deeper scratches or etchings. Whatever the defect is, the goal is still the same and that is to only remove as little paint as necessary to remove the defect so you leave the most amount of paint on the car so it will last over the service life of the car.

    Now follow me on this...
    When you sand in a repeatable pattern, for example straight-lines, you have some measure of control over the pattern of sanding marks you're putting into the paint and also the number of strokes and thus the amount of material being removed. If you sand in random, overlapping circles you have realistically no control over your sanding mark pattern and little or no way of gaging how much paint you're removing while you're sanding. Wet-sanding paint is already difficult and risky, there's no good reason to make it more difficult or more risky so I'm not going to recommend sanding in circular motions and common sense dictates to also avoid sanding in circles.



    Big Picture
    Of course the big picture goal is no matter how you sand the paint, in the end you remove ALL sanding marks and then there isn't any issue with which method you used. This is easier said than done and paint hardness is a crucial factor as to how easy or difficult it will be to buff out the sanding marks and film-build or paint thickness will be the limiting factor as to how much paint you can remove with both the sanding and the buffing process. (So be careful).


    Personal Preference
    Because in my life I've met seasoned Professionals that are proponents of both methods, choosing the best method becomes a personal preference. As long a there's enough paint or film-build on the car to work with then theoretically, both methods will work.

    Ultimate Goal - Leave the most paint on the car
    The most important part of any hand sanding project is to use the highest quality finishing papers you can obtain as this will reduce the potential for uneven sanding marks while leaving the most amount of paint on the car and making the removal process faster and easier.

    Machine Sanding
    And in this writer/detailer's opinion, generally speaking, machine sanding is a better option than hand sanding as it will leave more uniform sanding marks that will be a lot easier to remove and the machine compounding process will always be faster and easier versus trying to remove hand sanding marks.


    Related Topics
    Wet-sanding - Fresh Paint vs Factory Paint
    Basic Hand Sanding Techniques
    How long will a half sheet of wet/dry sandpaper last before it stops cutting and you need to replace it?
    RIDS and Feathersanding - A Highly Specialized Technique by Mike Phillips
    Removing Orange Peel & Sanding Marks with the Griot's ROP and the Wolfgang Twins

    Related Tools
    Meguiar's Unigrit Sand Papers 8 Sheets - Mix and Match Grit Sizes


    Defelsko PosiTest DFT Combo Electronic Paint Thickness Gauge




    Direct Drive Rotary Buffers - Circular Polishers
    Easiest Rotary Buffer to learn how to use!
    Flex 3403 Lightweight Rotary Buffer
    11.5 Amps
    1100 to 3700 RPM
    5 Pounds
    1 Year Limited Warranty




    Tools & Accessories Quick Reference List

    Here's a Quick Reference List that will take you to the different categories of products related to machine polishing

    Electric Buffers - Main Landing Page for everything in this list.
    Buffing Pads for Dual Action Polishers
    Buffing Pads for Rotary Buffers
    Buffing Pads and Accessories for the Cyclo Polisher
    Bonnets
    Hook And Loop Backing Plates
    Grit Guard Universal Pad Washer - Foam Pads and Wool Pads - All Machines
    Autogeek System 2000 Pad Washer for Rotary Polishers Wool Pads and Rotary Buffers
    Brinkman Maxfire Dual Xenon Rechargeable Spotlight
    Autogeek Detailer’s Tool Bag
    Pinnacle Detailer’s Tool Bag
    Wolfgang Detailer's Tool Bag
    Defelsko PosiTest DFT Combo Electronic Paint Thickness Gauge
    DP Polishing Pad Rejuvenator
    Defelsko PosiTest DFT Combo Electronic Paint Thickness Gauge
    Foam Pad Conditioning Brush
    Duo Spur Wool & Foam Pad Cleaning Tool
    Pinnacle XMT Polishing Pad Cleaner
    Pinnacle XMT Polishing Pad Conditioner




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  2. #2
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    Re: Two Schools of Thought - Sanding in Straightlines or in a Crosshatch Pattern

    whats wrong with circular motion?

  3. #3
    Mike Phillips
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    Re: Two Schools of Thought - Sanding in Straightlines or in a Crosshatch Pattern

    Quote Originally Posted by Misha View Post
    whats wrong with circular motion?
    Great question!

    If you move your hand in a circular motion with sandpaper on paint you will scour the paint with circular scratches. A scoured finish will be the result but the worse problem is it's going to be hard to monitor how much paint you're removing off a section and thus off a panel and extrapolated out, off an entire car because you have little or no control or knowledge of how much paint you're removing with random, overlapping circular hand motions when sanding.

    If you read the first post, there's section called, Related Topics, under this section is a thread that discusses technique, maybe take a moment to read it for form information on the topic of hand-sanding.

    Related Topics
    Wet-sanding - Fresh Paint vs Factory Paint
    --> Basic Hand Sanding Techniques <--
    How long will a half sheet of wet/dry sandpaper last before it stops cutting and you need to replace it?
    RIDS and Feathersanding - A Highly Specialized Technique by Mike Phillips
    Removing Orange Peel & Sanding Marks with the Griot's ROP and the Wolfgang Twins


    Have you ever wet-sanded a car by hand?



  4. #4
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    Re: Two Schools of Thought - Sanding in Straightlines or in a Crosshatch Pattern

    Quote Originally Posted by Mike.Phillips@Autogeek View Post
    Great question!

    If you move your hand in a circular motion with sandpaper on paint you will scour the paint with circular scratches. A scoured finish will be the result but the worse problem is it's going to be hard to monitor how much paint you're removing off a section and thus off a panel and extrapolated out, off an entire car because you have little or no control or knowledge of how much paint you're removing with random, overlapping circular hand motions when sanding.

    If you read the first post, there's section called, Related Topics, under this section is a thread that discusses technique, maybe take a moment to read it for form information on the topic of hand-sanding.

    Related Topics
    Wet-sanding - Fresh Paint vs Factory Paint
    --> Basic Hand Sanding Techniques <--
    How long will a half sheet of wet/dry sandpaper last before it stops cutting and you need to replace it?
    RIDS and Feathersanding - A Highly Specialized Technique by Mike Phillips
    Removing Orange Peel & Sanding Marks with the Griot's ROP and the Wolfgang Twins


    Have you ever wet-sanded a car by hand?



    yeah, M3 last weekend. owners brother decided it was ok to move stuff near silver M3 and got couple scraches. just did that, owner will be back for full detail in spring



    have to get after pics from my friend since i forgot to take them. but scraches are gone (used 1000,2000, 3000 grit sand paper, powergloss with purple wool and 203 with orange pad)

    although i see your point about one direction. will have to try that next time. have to wetsand my hood after filling paint chips from road rocks. so gona practice on that

  5. #5
    Mike Phillips
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    Re: Two Schools of Thought - Sanding in Straightlines or in a Crosshatch Pattern

    Quote Originally Posted by Misha View Post
    whats wrong with circular motion?
    Quote Originally Posted by Mike.Phillips@Autogeek View Post
    Have you ever wet-sanded a car by hand?
    Quote Originally Posted by Misha View Post
    yeah, M3 last weekend.

    Did you move your hand in circular motions when you were sanding?


  6. #6
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    Re: Two Schools of Thought - Sanding in Straight-lines or in a Crosshatch Pattern

    yep. did circular motion, but i see how one with same direction could have worked better

  7. #7
    Regular Member SuperSport's Avatar
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    Re: Two Schools of Thought - Sanding in Straight-lines or in a Crosshatch Pattern

    When restoring my chevelle and a few other cars me and my dad did most of the body work. On long panels you get to the point before paint where you are doing a lot of block sanding. This is to ensure that your panels are not wavy and look more like a sheet of glass opposed to a wavey mess. You can really tell when this step is not taken. After these cars are painted I always wet sanded pretty much the same way. I used long even straight line strokes. I always heard that you wanted the clear as even as possible just like when blocking. Now this is where my question comes. Wouldn't any other method leave high and low spots? Wouldn't this, like not block sanding before paint leave a wavyness, or is the clear coat so thin that it really will not show to the human eye?

    1967 Chevelle SS
    2004 Nissan 350Z
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  8. #8
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    Re: Two Schools of Thought - Sanding in Straight-lines or in a Crosshatch Pattern

    got megs sanding block thingy ( http://www.autogeekonline.net/galler...riment1025.jpg ). gona be sanding my hood. cant wait to see how it will turn out, then will have to get 3m clear bra to prevent rock chips again

  9. #9
    Super Member Flash Gordon's Avatar
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    Re: Two Schools of Thought - Sanding in Straight-lines or in a Crosshatch Pattern



    Quote Originally Posted by SuperSport View Post
    When restoring my chevelle and a few other cars me and my dad did most of the body work. On long panels you get to the point before paint where you are doing a lot of block sanding. This is to ensure that your panels are not wavy and look more like a sheet of glass opposed to a wavey mess. You can really tell when this step is not taken. After these cars are painted I always wet sanded pretty much the same way. I used long even straight line strokes. I always heard that you wanted the clear as even as possible just like when blocking. Now this is where my question comes. Wouldn't any other method leave high and low spots? Wouldn't this, like not block sanding before paint leave a wavyness, or is the clear coat so thin that it really will not show to the human eye?

    I prefer to sand in straight lines too
    “Hard times create strong men, strong men create good times, good times create weak men, and weak men create hard times.”

  10. #10
    Super Member Flash Gordon's Avatar
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    Re: Two Schools of Thought - Sanding in Straightlines or in a Crosshatch Pattern

    Quote Originally Posted by Misha View Post
    whats wrong with circular motion?


    What about when your using sanding disks?
    “Hard times create strong men, strong men create good times, good times create weak men, and weak men create hard times.”

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