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Avoiding Cornrows

A lot of techs have problems with "corn rows" in their dents. For those that may not be familiar with this term, corn rows are those parallel rows of micro ridges and creases that many techs see as soon as they cross check their dents. The main reason they aren't seen until you cross check, is because light runs right through the micro ridges and valleys when they are perpendicular to your reflective source, because there is little for the light to reflect off of. This makes this area of the dent look fairly uniform, even though it isn't. When you cross check by moving the board 90 degrees, you see the rows because the light is now reflected off the ridges and valleys, the light can no longer run right through them. See illustration #1.

Most often, the tech who gets corn rows is bringing the dent up too fast with overly aggressive pushes, instead of bringing it up in level stages. Also, after the core of the dent is somewhat removed, the tech is probably making many pushes that are too aggressive, in a straight line perpendicular to the reflective source. In other words he works the dent from front to back, and back to front. See illustration #2.

Many techs rush the repair process, wanting to get the dent up and looking good as soon as possible. They push wherever they see they have a low, and pay little attention to the pattern, or tool pressure they use. A dent may look like it is coming up faster, and cleaner if the tech pushes harder than he should, and perpendicular to the reflective source. Again, this is because, the light will pass through slight lines of pushes that are perpendicular to a dent. So a lot of techs will subconsciously push perpendicular {front to back on a hood}, because the dent looks good fairly quick. But as soon as they cross check they wonder why they always have those rows, to deal with.

Depending on how many of these perpendicular pushes were made, and how high and tightly spaced these rows are, the tech can spend lots of time bringing the dent back to perfection. Typically a tech is told to make sure he frequently cross checks his dent while working to prevent this from happening. This will work, and is a good idea for a newbie tech. Cross checking many times during the removal process will catch most corn rowing before it becomes a problem. However, constant cross checking really isn't necessary, if you use the right repair methods. Even if a tech moves their board frequently during the removal process, they may still find themselves chasing this corn row effect back and forth, each time they move their board if their pushing technique is wrong.

To review then, the basic problems are, not bringing the dent up in level stages, pushing too aggressively, and an improper pushing pattern. So what do you do?

See illustration. #3

I'm not saying you need to make a fetish out of your pushing pattern. What I am saying is try to work your dent in a more parallel pattern to your reflective source, and avoid pushing perpendicular. When you cross check your work, don't forget to avoid pushing perpendicular, you still need to push parallel to your board to help avoid making any new rows.

Of course the same principles apply to doors. Bring the dent up slowly, and level, in small stages. After the bulk of the dent is up, work the dent in a pattern parallel to your board {which will be up and down the door if your board is parallel to the front or rear edges of the door}. Avoid working in a perpendicular pattern {which will be front to back if your board is parallel to the front or rear edges of door}. See illustration #4.

By the way have you ever noticed that corn rowing is more common in horizontal panels than side panel work? This is because most of the time you work a dent in an up and down pattern on the door and most of the time this is parallel to the reflection board. Most of the time, working a door in a parallel pattern to the light is natural. Many techs have to fight the natural instinct to push perpendicular on hoods though, and focus on pushing parallel. This doesn't come naturally for most techs.

At first, all this will take some effort, especially if you have developed these habits over a period of time, and are used to working this way. But eventually, it should become second nature to you, and you won't even have to think about it. You will find that working this way will greatly improve your overall quality and speed. This method will also reduce your need to constantly cross check your dent. Of course cross checking is always necessary when finishing your dent, especially on horizontal panels that can be seen from 360 degrees. The more angles you cross check from to finish, the better your final product will be.

If you have any questions or comments about this article please post them in the PDR section.