Looking for an abrasive type for a consistent, finished sheen

[rnt80]

I am currently working on a built in that has a 16' long mdf counter that is approximately 20" deep.  I am having some difficulty in getting a consistent topcoat (I'm spraying KemAqua Plus tinted white) with my MiniMite3.  I've sprayed it moving along the length and I've also sprayed it making a million passes front to back, making my way down the counter.  Regardless of the direction I'm still ending up with stripes when look at the counter at an angle.  I typically don't use any abrasives above 360 and was wondering if there was an abrasive that I could use, or work up to, that would provide a consistent , satin level sheen across the counter top.  I'm not a novice when it comes to finishing but I'm certainly no expert.  The only place I can spray this piece is in my backyard and here in AZ it is currently 65-70 degrees outside when I spray it.  With all of this considered, plus the fact that I've already put down four coats on top of the primer, I'm not that optimistic that I'll be able to spray a coat without stripes. The back edge of the counter will be covered with uppers so that is why there is an unpainted strip along the back.

 

[Scott B.]

I don't think it is an abrasive issue. I think it is either the dial in on the gun, or you are flashing yourself by rewetting sections that are tacking more quickly than you are ready for.

Is this a gun and product combo you have done much with in the past?

 

[rnt80]

Scott, I should've been more specific.  I believe the flashing is the problem.  This is the second job I've used the set up on and for the most part it has gone well.  At this point I was hoping to essentially "polish" the counter top by cycling through some abrasives.  I've done some larger pieces for this job but this counter is huge (16' long) and I'm not sure that my lack of expertise coupled with a less than desirable spraying environment is going to get me the results I demand.

 

[Scott B.]

Scott, I should've been more specific.  I believe the flashing is the problem.  This is the second job I've used the set up on and for the most part it has gone well.  At this point I was hoping to essentially "polish" the counter top by cycling through some abrasives.  I've done some larger pieces for this job but this counter is huge (16' long) and I'm not sure that my lack of expertise coupled with a less than desirable spraying environment is going to get me the results I demand.

I do believe it could be polished out. That is something that takes a bit of training and practice, though.

 

[rnt80]

Do you have a recommendation for progression of abrasives?  I have some other pieces that are already sprayed that I can practice on.

 

[tjbnwi]

Russ,

What sheen is the KA+?

If you have an RO sander---random sand @ 1200-1500, 2000 Platin--5000 polish-11,000 polish.

Depending on the sheen you may not have to use the 11,000.

Tom

 

[rnt80]

Tom, it is a custom match, low gloss, akin to a satin.  I have a RO150 that I've been using with some granat 360 between coats.  I'm happy with the KA+.  As I mentioned I think it has everything to do with my lack of ability and the environment in which I'm spraying.  If I can mitigate those things by buffing this out then that's the way I'll go.

 

[tjbnwi]

Sand with the 1500 Granat, buff with 2000 Platin, it should maintain the sheen you want.

Tom

 

[Iceclimber]

Im sorry paint problems like this can be a real bummer.

Wish i had something more to offer in the way of help. My only concern with polishing it out is that you might end up with two different sheens. I also would not be surprised if this is not due to the air settings on the gun and or how the paint is or is not thinned before spaying. That kinda thing combined with warm temperatures or going back into a area you already sprayed and or the direction the you start spraying in vrs finish from with regard to things like where will the overspray or spray mist land are all factors when stuff like this happens.

Also i would never consider spraying any interior finish grade project outside. Thats just me though. After all the work i put into building something I'm not about risk ruining it finishing it.

If you can before it is installed and you live with something that is going to bother you for the rest of your life i would just take it to a shop with a spray booth and let them shoot it. Even better is find someone that will let you use their booth.

 

[jhn_gdfry]

You could always use a reducer in the KA. It'll slow the flash and allow it to flow out. Also, I've had issues with mdf coming up "patchy".  No matter how many times it went through the thickness sander or was primed, topcoat always came up spotty. Hope it helps.

 

[rnt80]

Im sorry paint problems like this can be a real bummer.

Wish i had something more to offer in the way of help. My only concern with polishing it out is that you might end up with two different sheens. I also would not be surprised if this is not due to the air settings on the gun and or how the paint is or is not thinned before spaying. That kinda thing combined with warm temperatures or going back into a area you already sprayed and or the direction the you start spraying in vrs finish from with regard to things like where will the overspray or spray mist land are all factors when stuff like this happens.

Also i would never consider spraying any interior finish grade project outside. Thats just me though. After all the work i put into building something I'm not about risk ruining it finishing it.

If you can before it is installed and you live with something that is going to bother you for the rest of your life i would just take it to a shop with a spray booth and let them shoot it. Even better is find someone that will let you use their booth.

Tom, thanks for your advice and help.  I'll order the abrasives and try them on my samples. 
All of my spraying is done outside.  I really don't have another option and while I'm not a finishing pro my results thus far, in less than desirable conditions, have been good.  I want to move the counter as little as possible so I'd be hesitant to load it up to take it to get sprayed, bring it back home, and then load it up again for the install.  If buffing it out doesn't work then that may be what I have to do.

 

[tiralie]

Spray a wetter/thicker mil. coat on the main field, avoiding the profile so you don't get pooling and drips.
KM is fairly forgiving, and settles well even when sprayed with a "heavy hand". I've noted that when I sprayed it outside I got some slight striping as well, but I was using a pressure pot and had my fluid volume turned down more than usual.
Your temperatures are good.
Tim

 

[tjbnwi]

Russ,

I believe you can top coat the KA+ white with KA+ clear. I have MRE and BRE in stock. I can send you a quart or two of either of you want to try it. (I'll check to make sure you can use clear over the white).

I top coat pInt on railings with KA+.

A side note, some asked on another forum if you can brush KA+, I tried it on a drawer, worked very well. Have to avoid over brushing so it flows out. Biggest drawback was it took me longer to brush one drawer that shoot the other five.

Tom

 

[rnt80]

Tom, that's very generous of you.  I have a gallon of KA+ clear in MRE that they gave me when I was first trying the product out.  I think you're correct that it can be sprayed over the white, I'm pretty sure I read that in the product literature.  I may try that on the samples that I have and see how it turns out.  When I use Target's tinted white lacquer I topcoat it with their poly.  While I love the smooth finish that results too much of it will yellow the finish.

 

[tiralie]

I've sprayed it moving along the length and I've also sprayed it making a million passes front to back, making my way down the counter.  Regardless of the direction I'm still ending up with stripes when look at the counter at an angle. 

Temperature (allowing the coating adequate time to level) removes all the problems I have had with striping etc. I am spraying either very early in the AM daybreak or later in the evening (after 6 pm) and this is allowing the coating to level perfectly.

I have sprayed Kem Aqua outside and got stripes as well and recently sprayed it inside a home with excellent results. I have been spraying a tinted white base ML Campbell - Agualente in a very warm >75F/24C spray booth and have been having the same results.

Tim

 

[Bohdan]

I've also sprayed it making a million passes front to back, making my way down the counter.

Have you tried making your way up the counter i.e. spray so that the wet coat goes over the overspray.

 

[Mr Heavy]

I have a sneaky suspicion it's actually partly a sealing issue.
If you're using a shellac-based primer then I'm wrong, if you're not, might I suggest trialling a dummy section with Zinsser B-I-N Shellac-Based Primer White or whatever's available in your part of the world?

I know it's supposed to be - sol as - an anti-bleeding agent, but it'll also homogenise the surface absorption rate of whatever goes on top of it. From what I've read of the thread, that not having been stabilized would seem a likely culprit.

 

[tiralie]

I have a sneaky suspicion it's actually partly a sealing issue.

After four coats and a primer with sanding between coats I think it's sealed...but I could be mistaken...