What things might cause "waves" in a finished paint project.

MJM

Promoted Users
Was reading another thread and it was mentioned that sanding on one spot would causes a wave on the panel. I understand this, makes sense.

What other actions could cause a "wave" (s) on a finished panel?
 

Barry

Paint Fanatic
Staff member
One of my most common calls from hobbyists.
I wetland and buff, now I have urethane wave, the first question did you have it before you wet-sanded? No, most of the time.
You have a new soft clear and say you do a door blocking clear like you do 2k primer on an angle; just one extra stroke in the center of the door will mess up your perfect job.
 

Gmills

Promoted Users
I'm fairly new to this too only having done two restorations. I have been fairly pleased with what I have done so far but always look to improve. Barry, if color sanding a door like you mentioned would the preferred direction be front to back or top to bottom? Just depends on what the shape of the panel is? Reason I ask is I recently did an early bronco and I know I had it blocked straight but I'm not totally satisfied with the tops of the quarters. The upper part of the panel is say 5' long but only 8" tall and I sanded vertically. There is a little wave I may have caused since I sanded the short direction.
 

Chris_Hamilton

Trying to be the best me, I can be
I'm fairly new to this too only having done two restorations. I have been fairly pleased with what I have done so far but always look to improve. Barry, if color sanding a door like you mentioned would the preferred direction be front to back or top to bottom? Just depends on what the shape of the panel is? Reason I ask is I recently did an early bronco and I know I had it blocked straight but I'm not totally satisfied with the tops of the quarters. The upper part of the panel is say 5' long but only 8" tall and I sanded vertically. There is a little wave I may have caused since I sanded the short direction.

I like to travel the longest length of the panel. Example, for a door you would go front to back rather than top to bottom. Same with a hood or roof or quarter. Just go back and forth, trying to sand each panel as evenly as you can. Never stay in one area trying to remove a defect. Keep sanding the entire panel until the defect is removed.
 

sprint_9

Rookie
Ive found being gun shy leading to more visible wave. By not being aggressive enough color sanding you still sand off the orange peel but ride over any urethane wave. The wave will become more apparent once the surface becomes more reflective.

On my truck it looks like two different people painted the front half vs the box. In essence it was because my attitude was totally different. When I painted and finished the first half I wasn't as gun shy about sanding and had a booth still set up to fix any mishaps. By the time I got to my box time had ran out and my booth was gone, no more easy fixes, any mistake would have been a major undertaking to correct so a less aggressive approach was taken and it shows.
 
Another issue not often mentioned is pressing too hard on the sanding block. It can cause the panel to give some and even though it removes the guide coat, the panel returns to it's normal position and there remains a very slight high spot.

Now I see Metalman did mention this as well.
 

jcpettit

Promoted Users
I like to travel the longest length of the panel. Example, for a door you would go front to back rather than top to bottom. Same with a hood or roof or quarter. Just go back and forth, trying to sand each panel as evenly as you can. Never stay in one area trying to remove a defect. Keep sanding the entire panel until the defect is removed.
Funny that I came across this thread. I am actually in the process of color sanding a 72 cuda. I am normally a collision guy so all of my jobs are pretty much just nib sanding. This is actually my first job requiring this much detail. Yesterday I was going to start color sanding the roof with a block and was hesitant on which direction to go, because the roof is almost perfectly square. Which direction would you think in a situation like this?
 

theastronaut

Promoted Users
Soft sanding blocks in the bodywork and initial colorsanding steps will make the panel smooth but not straight. The "give" in the surface of the block acts like suspension on a car and absorbs the high spots instead of knocking them flat.

Using a block that is too short to span enough of the panel to make it an even shape.

Using a block that isn't flexible enough to conform to the overall shape of the panel.

Worn out sandpaper that doesn't cut efficiently will round over high spots instead of cutting them flat.

Using sandpaper that is too smooth when doing bodywork or initial colorsanding- smooth paper is only for smoothing. You need rough paper to shape the panel flat first before you try to make it smooth enough to paint. The same goes for clear- the paper needs to be aggressive enough to cut any texture or urethane wave flat.
 
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