What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Tip: Cutting and Buffing Paint

Cured paint allergy, anyone?

Since I started the cut and buff process in earnest, I have ruined many tee shirts and shorts with the paint slurry that gets slung out of the random orbital sanding pad - you would think that the fine sanding particles of cured paint would be inert enough to wash right back out of the cotton fabric when laundered. You would be wrong, too ;). The stuff has the staying power of RIT dye.

I have also noticed my hands starting to itch intensely off and on throughout the day without any signs of dryness or rash, flaking or redness. I wondered what environmental things might be triggering this since I have done a lot of odd jobs around the house this past week, up and down ladders, etc. But my suspicion keeps returning to the paint sanding residue as the likely offender. I had noticed a tendency for my arms to get itchy and red the last few times I did composite layups (could I finally be developing an epoxy allergy after 30 years of fooling with RV's ?!). Now I'm pretty sure I'm showing some kind of allergy to the paint particles generated by the wet sanding process. Anybody else had this happen to them? I'd hate to have to wear nitrile gloves while sanding but I will if it will fix this itch.

After 40 (okay, 39) years in primary care medicine, I should be answering instead of asking this question :D but I really am curious if what I suspect is going on with me has happened to anyone else.
 
Cut and buff

I always wear nitrile working around paints. I don't want finger oils anywhere. I wear work gloves with fiberglass to keep from cutting myself in shards.
 
I started getting itchy forearms working with epoxy, so I bought a box of plastic disposable gauntlet sleeves like the food workers wear. Glove, and then the gauntlet over the glove cuff up to the elbows. Solved the problem
 
I started getting itchy forearms working with epoxy, so I bought a box of plastic disposable gauntlet sleeves like the food workers wear. Glove, and then the gauntlet over the glove cuff up to the elbows. Solved the problem

I used barrier cream and it has been an excellent solution for me when cutting piles of fiberglass. Gloves for epoxy for sure.
 
Well, I took the evening off from wet sanding tonight as I'm out of 1/4" masking tape to put over the rivet lines and it's not for sale anywhere in this town, so... Amazon delivers Wednesday. In the mean time, the itching of the hands has finally settled down enough to where I can probably get to sleep tonight. Just one data point, but it's in the confirmatory direction so far...

After 7 years I've become allergic to my daggone airplane. :rolleyes:
 
Arm shields

Thanks for the tip. Done. They will arrive Thursday if the supply chain holds.

Wonder what, if anything, I should use to keep the stuff off my belly & tee-shirts. Maybe a trash bag poncho with holes for my neck and arms. But I don't itch there - only my hands, and a little on the forearms.
 
I wear an old machinist’s apron. Has a nice line of compound across it, lol.
I probably use too much, but I don’t like it to get dry and hot. Fiberglass parts are especially prone to getting too hot since they don’t dissipate heat.
 
Sounds like you have a routine worked out, and some valuable experience here.

How much do you charge for a complete cut and buff, Mike? I might opt to sit back and watch you do it for me!
 
I'm mostly satisfied with results of my initial cut and buff on the upper surfaces of both wings. What I'm learning from a detailed inspection of my work to date is that I probably tend to rush the 1500 grit Trizact wet sanding step, as the final result has a lot of fine curly-cues visible. Going back and re-sanding a small area with 1500, 3000, compound and polish gets rid of these at the cost of considerable extra re-work. The swirlies are probably there from the 1000 grit dry sanding with the 3M purple film sheets, or else I'm getting widespread contamination of the 1500 Trizact's with foreign grit, which I doubt. The nice thing about this process is that there is no rush with it, and no harm in going back at any future time and improving on what I'v already accomplished.

For those with lots of orange peel to remove and who are confident in the thickness of their base paint coat, I offer the following initial step I found on the internet. This will speed things along and save lots of money on finer grades of abrasives that would tend to clog up and take forever to git-er-done:
 

Attachments

  • 035_JPG-2477668.jpeg
    035_JPG-2477668.jpeg
    48.7 KB · Views: 140
In my experience, the pigtales (fine curly-cues) are due to contamination. You have to watch for those as you progress through each step. If you see them, you have to backup and clean everything carefully. You have to get rid of them before going to the next step.
Stewart Willoughby, 6
 
You may be right, Stoo. I wet-wipe everything down with a sopping towel and then dry off with microfiber before commencing the next step. Until the polish stage starts to bring up the shine, the pigtails from the random orbital are not easy to appreciate, making it really hard to tell when you've sanded enough to move to the next step.
 
Be sure to also check the sander disc for any clogging, etc. Minor buildups can be scraped off with a straight backed razor blade. Then rinse the disc well.
Stewart Willoughby, 6
 
The swirlies are probably there from the 1000 grit dry sanding with the 3M purple film sheets, or else I'm getting widespread contamination of the 1500 Trizact's with foreign grit, which I doubt.

Dry sanding might do it. I use 800 if I need a heavy initial cut, but it's done wet.
 
Thanks for the tip. Done. They will arrive Thursday if the supply chain holds.

Wonder what, if anything, I should use to keep the stuff off my belly & tee-shirts. Maybe a trash bag poncho with holes for my neck and arms. But I don't itch there - only my hands, and a little on the forearms.

Try this....
apron.JPG
 
Dry sanding might do it. I use 800 if I need a heavy initial cut, but it's done wet.

I was wet sanding for awhile with the 1000 grit purple film disks from 3m/Amazon, before I discovered they're meant for dry use only. :eek: Didn't seem to make any difference in the level of pigtails I saw later in the process. One thing I've come to like about the dry sanding is it's faster to accomplish and much easier to see how much of the orange peel texture has been eliminated with each pass, since there's no need for a wet wipe-down and drying off to check progress. A quick swipe with a dry microfiber towel to dust off the work piece and you can see exactly how far you still have to cut before the next-finer stage.

I'd prefer to stick with it if I can, but if the dry sanding makes for extended 1500 wet sanding sessions to get pigtails out, I may rethink it and find some 800 or 1000 Hookit wet abrasives somewhere.
 
Question for Dan

... or anyone else with experience with blending.

I have had good success with cut and buff efforts overall. But as I progress with this part of the project I am having a few uh-oh's where I ve cut through a rivet edge, panel edge or even an outside radius on a compound curve such as shown below, with accidental exposure of primer or in some cases bare metal or resin. I anticipate having to fix these boo-bo's with a spot paint repair using an airbrush.

Since I've heard it talked about that blending of a spot repair versus repainting an entire panel is a skill all its own, I wonder if there are some pointers that might tip the odds in my favor for an acceptable outcome. Any advice appreciated.

(The cowl was a dull orange peel when I started and came out beautifully, except where I accidentally exposed primer here and on a few edges).
 

Attachments

  • 68211467244__27A17001-7AF4-4728-B91D-FBA0371CB726.jpg
    68211467244__27A17001-7AF4-4728-B91D-FBA0371CB726.jpg
    226.5 KB · Views: 137
Yeah, it happens. Fiberglass and curves like that are susceptible since the fiberglass overheats easily and it's hard to judge how deep you are cutting on rounded parts. You have to be really careful on fiberglass. Stop and feel the temperature often. Keep a spray bottle of water handy.
Quite frankly, when I've done that, I re-shoot the whole panel. For rivets and edges, you can touch-up with a brush. My spinner has, well, let's just say, more than a few coats. Looks awesome now! Next to last time, I was buffing the last little area, overheated it, and a spot of paint just popped off. Gaaaaa! Wet sand, primer surfacer, sand, back in the booth.
Since you still have some pinholes , this would be an opportunity to make some improvements there. Some primer-surfacer, sanding, and a re-shoot.

None of this is easy. I've got six weeks into paint correction stuff. I called it "done" this weekend, but it's really not. Those paint jobs you see that look perfect didn't come out of the booth looking like that. They have teams that "fix" them.

Hang in there. You'll have some parts that will be just perfect, and every time you look at them, you'll grin a little, since "you did that".
 

Attachments

  • 67803213663__D5C2948D-87C5-4183-B8AA-C01363637C93.JPEG
    67803213663__D5C2948D-87C5-4183-B8AA-C01363637C93.JPEG
    536.7 KB · Views: 120
Last edited:
Cut & Buff

I prefer hand working as much as possible. Its a lot more labor, but easier to control. I tape any area susceptible to cutting through like rivet lines and edges. Work them after.
 
I have had good success with cut and buff efforts overall. But as I progress with this part of the project I am having a few uh-oh's where I ve cut through a rivet edge, panel edge or even an outside radius on a compound curve such as shown below

I would not run a 1900 RPM buffer on a surface as highly curved as that inlet lip. Don't feel bad...I too learned it the hard way, buffing cars.

Like Mike said, most body shops just reshoot the whole panel.
 
To be more precise, this area appeared during the 1500 and 3000 Trizact stage and got only slightly worse with buffing and polishing compounds, done at 1200 rpm on the 7" buffer. It's a combination of the convex shape and that I probably unknowingly skimped on paint film thickness in this area...

Given that I'm near to exhausting the two gallons of red paint from Stewart, I'm going to try a spot repair here. If I have to reshoot the whole piece, I will likely have to order another quart of each of the two reds I mixed together to get this shade, and with shipping, even a quart of each runs into some money. If I were to repaint every panel that has or will have a blem from the cut and buff (in my hands), I would end up reshooting the whole plane, and that's not happening :D
 
..
Since I've heard it talked about that blending of a spot repair versus repainting an entire panel is a skill all its own, I wonder if there are some pointers that might tip the odds in my favor for an acceptable outcome. Any advice appreciated.

.

Not really in the novice category, but here you go:

single stage or base/clear? A burn through like that is very difficult to repair. Blending will be hard as well due to the placement of the blem. Generally speaking you spray the area as normal, but at the end of the area, you slowly tip the gun 90* away from perpendicular to parallel to the surface as the gun is travelling. This leave a progressively lighter pattern as it moves away and creates the "blending." Typically this is just done with base and the whole panel cleared again. If you want to experiment with this approach with clear or SS, then You then need to sand it back flat at the edges of the blending and buff. When done with clear, you add 40-50% reducer in with the clear. The objective is for the solvents to melt into the existing clear for better mixing / levelling. Most suppliers sell a special blending solvent that is stronger / more aggressive than reducer and does this better than reducer. Never worked with water based stuff so can't help on the nuances of that type or if it's even possible.

Strongly recommend practicing this approach on some scrap pieces. I am sure there are YT videos out there showing the technique.

In the future, strongly rounded edges like that should NEVER be done with a power buffer until you have MANY hours of experience. It is very easy to compound and polish them by hand with a rag. I tend to use a 3" pad on a variable speed drill and go slow on areas like that, but I have also done this many times. You probably know this, but NEVER buff an edge or rounded part with the pad spinning towards the edge. Alway spinning away.

IMHO this was not an issue of paint thickness. Think tangents. If you don;'t rock the sander quickly, you are heavilly concentrating on a very small area. Heavilly rounded parts like that should never be done with power sanders, as it is VERY easy to burn through something with a 1/2" radius. Instead use a medium density block. I sometimes just use my fingers in tight areas.
 
Last edited:
Is it better to cut and buff with single stage paint or does it matter at all?
I am using single stage paint.

There are different qualities of SS paint. Many do not use polyurethane pigments to keep cost down. SS paint is just clear with pigments mixed in. THey also use additives that force a complete layer of clear to form on the outer surface. That allows for only a small amount of cut and buff before breaking through that pure clear layer and into the pigmented clear. If you go too far and break through that layer, you start abrading the pigments. If those pigments are not polyurethane, you will see variations in the sheen/color. If PU pigments are used, you will not notice it even if you break through the upper layer. Read the data sheet and look for warnings about buffing too much.

If you are a novice and expect the need for aggressive cut and buff, I would suggest a layer of clear over the last coat of SS to give thickness to cut into. Don't even need to clean the gun; just pour the clear in and spray. That said, some formulations require a 24 hour period before other stuff can go over it, but with most you can spray the clear as soon as the last SS coat flashes off.

Larry
 
Last edited:
This is Stewart Systems single stage waterborne polyurethane.

The way I figure it, I will wade in and try my hand at an airbrushed, over-thinned topcoat and some very delicate use of abrasives to accomplish a repair. If it isn't acceptable, I'll order a new supply of paint and reshoot the entire piece. Little lost by trying. I do hope an airbrush deftly used will allow me to spot a few rivet head crescents that are peeking through on the fuel tanks. Anything is better than a shiny half-moon of aluminum staring at you from within that beautiful red.
 
If you are a novice and expect the need for aggressive cut and buff, I would suggest a layer of clear over the last coat of SS to give thickness to cut into. Don't even need to clean the gun; just pour the clear in and spray. That said, some formulations require a 24 hour period before other stuff can go over it, but with most you can spray the clear as soon as the last SS coat flashes off.

Larry

Thanks for all the info about SS paint. With regard to the clear coat, do I need to prep the SS painted surface before applying the clear, such as light sanding or can I apply the clear paint over the top? Most of my big panels were painted a few weeks ago so the SS paint has fully cured.
 
Thanks for all the info about SS paint. With regard to the clear coat, do I need to prep the SS painted surface before applying the clear, such as light sanding or can I apply the clear paint over the top? Most of my big panels were painted a few weeks ago so the SS paint has fully cured.

Too late for the easy way-as cross linking window is gone. If you want to CC now, it must me scuffed or sanded. Follow paint providers recommendation, but 400 grit is usually coarse enough and pads also work. At this point, I would do whatever you are going to do and look at the results and see if you are happy with them. You can always shoot a clear coat later if you don't like it.

The SS paints have varying ranges of quality and therefore ability to cut and buff. I would call the tech folks at your paint company (the manufacturer, not the dealer that sold it) and ask them about limitations for cut and buff. They will know how far you can go and what side effects exist if you go too far. The recommendation to shoot a coat of clear was based upon the assumption that it was easy to do and that is no longer the case for you.

Larry
 
Last edited:
Thank for the info in the clear coat. I was using SS to reduce the amount of work, with the exception of cut and buff. My DIY paint job will not win any award but I want to know about the CC option if I need to reshoot a panel at a later date. I think, and with some hope, I put enough layers to cut and buff and call it done.
It has been almost 2 months of priming, finish sanding, and painting, this is such of a major effort, more than I anticipated. I only spray in the early morning because the backyard is not climate controlled so the painting takes longer than someone who builds a dedicated paint shop.;) I can see why they charge so much money to paint your airplane
 
Well, I was sanding with 1500 and 3000 wet last night and this happened. I had placed many pieces of m asking tape in the work area to warn me away from spots that were getting too thin despite orange peel still visible. When I pulled the tape to go over the delicate area with one swipe of the 3000 grit prior to compound and polish, the tape lifted a couple of chunks of paint/primer off the composite/micro surface. This was most disappointing, especially given my high degree of confidence in the etch and scuff we did prior to priming.

Because I did a thorough blended transition between canopy top and aft top skin, this is not a well-defined panel that can be repainted without tape lines, unless I do the entire top again. So I am considering attacking this boo boo with roller-applied primer and SS color. It all has to be sanded again to blend it anyway, so how much worse can it be to start with paint that has a roller texture vs sprayed? And with roller application I'll have good control of where it's applied without having to mask off, nor worry about overspray.

Planning to get some skinny hot dog foam rollers and give it a try; will certainly post my results here, for better or worse.
 

Attachments

  • 68238560755__626E0463-87E8-4329-A8F6-084A307BDF1A.jpg
    68238560755__626E0463-87E8-4329-A8F6-084A307BDF1A.jpg
    197.5 KB · Views: 138
This was most disappointing, especially given my high degree of confidence in the etch and scuff we did prior to priming.

You say sand and etch. Did you use chemical etching products on the epoxy or fiberglass? Chemical etching products are designed for metal and should never be used on porous surfaces like F/G or fillers, as they can retain the acid in their pores and cause bonding issues.

Larry
 
That may be a part of my issue, Larry. During the etch we went over the whole plane with Stewart etchant in spray bottles and scuffed the etch with Scotchbrite on a Velcro DA sander before flooding it off and drying. We did the aluminum skins this way, not intentionally "etching" the fiberglass, but some overlap of etchant slurry onto the composite surfaces was unavoidable.
 
That may be a part of my issue, Larry. During the etch we went over the whole plane with Stewart etchant in spray bottles and scuffed the etch with Scotchbrite on a Velcro DA sander before flooding it off and drying. We did the aluminum skins this way, not intentionally "etching" the fiberglass, but some overlap of etchant slurry onto the composite surfaces was unavoidable.

Looks like the adhesion loss is in a blend area between Vans glass and aluminum. The exposed area is sort of yellow in color. What are we looking at there?
.
 
Last edited:
Exactly, Dan. It's micro slurry over the transition/blend area between canopy top and tail cone skin on a -10. It was scuffed with red Scotchbrite prior to priming. Months before that it was wet block-sanded with 400 as part of the pinhole filling process with neat epoxy per your routine.
 
Exactly, Dan. It's micro slurry over the transition/blend area between canopy top and tail cone skin on a -10. It was scuffed with red Scotchbrite prior to priming. Months before that it was wet block-sanded with 400 as part of the pinhole filling process with neat epoxy per your routine.

But what is the yellow material? Microballoons are white (glass) or dark red (phenolic). White, and here just a trick of the light?
 

Attachments

  • Peel.jpg
    Peel.jpg
    71.1 KB · Views: 113
Fresh micro is white. 2-3 year old West Systems micro that's been flown unpainted is definitely somewhere between ivory and yellow. This has been my experience across two airframes and 20+ years.

Here's a picture of the etch and scuff in process just before primer went on. All the micro filler visible here was white originally. Pretty sure what we are seeing is not a trick of the camera, but the color of aging epoxy...
 

Attachments

  • 67539183282__7A2119EE-6633-4986-A55B-BBA43653313C.jpg
    67539183282__7A2119EE-6633-4986-A55B-BBA43653313C.jpg
    362.4 KB · Views: 119
Thanks for the clarification. So West and micro for shape, followed by a West skim to seal, then sanded, then flown a while.

At painting time, did you scuff the West areas again? Following the EkoEtch, which may have got on the epoxy-sealed micro, then was it EkoPrime or EkoPoxy? Any interim steps?

The instructions, such as they are, don't mention avoiding composites contact...

https://stewartsystems.aero/wp-content/uploads/EkoEtch-Instructions.pdf

...but this note appears on the order page:

EkoEtch is only for aluminum and should not be used on any other substrate.

Perhaps it would be worth calling for more information. In my limited experience, adhesion problems only get worse with time. If it pulls with masking tape, it's not well adhered. Better to know now and fix once.
 
We scuffed the whole airframe with Red Scotchbrite - the fiberglass was done dry and the aluminum was done wet with sprayed on Eko Etch. Pressure washed afterward to remove.

Priming was with Eko Poxy.

Good point about possible broader adhesion problems coming to light later. I'll reach out to Stewart and see what they say.

Thank you for the input, Dan.
 
We scuffed the whole airframe with Red Scotchbrite - the fiberglass was done dry and the aluminum was done wet with sprayed on Eko Etch. Pressure washed afterward to remove.

.

How much dry time on the F/G before paint? I know that water borne W&G remover only needs a couple of hours to dry on metal, but I have always been recommended to give filler or fiberglass 12 to 24 hours for full dry, due to the porous nature unless you can get it in the sun. I generally use solvent based W&G remover on F/G parts for this reason. Its a challenge, as you want to get the paint on AL as soon as possible after scuffing, but need to deal with evaporation times.

Larry
 
Last edited:
W&G remover

I use Kirker 600. Wipe with a soaked rag. Wipe it off with a dry rag. Wipe with a tack cloth and shoot.
 
I use Kirker 600. Wipe with a soaked rag. Wipe it off with a dry rag. Wipe with a tack cloth and shoot.

That is a solvent based product. Given that stewart is water borne, I speculate that they use water based W&G. Dry times very different between water adn solvent based.
 
Stewart does indeed have a water based degreaser. They even specify tack rags must be a brand compatible with WB products.

As to drying times we allowed, I cannot from memory answer that question as it's been months since the painting marathon was slogged through. Sorry. It's a pertinent consideration, for sure.
 
A quick question on cleaning up

I've managed to get rubbing/polishing compound "sling" on my transparencies. Even with the slow-start buffer, it was easy to do. These little splatters have dried into tint hard bumps on the windscreen that do not scrape off easily with a fingernail and are still adherent after going over them with a wet microfiber towel and attacking them a little more aggressively with Plexus polish and with Novus polish No. 1.

I suppose I could attack this with Novus 3, 2 and 1, as in a complete restoration, but I was wondering if there is a safe solvent that might re-suspend this compound so it would wipe off as it would when freshly wet. Diesel fuel? Kerosene? Naphtha? I don't want to damage anything by a hasty shortcut.

Tips appreciated.
 
You've identified a problem not seem in body and detail shops...plexiglass. Obviously not an issue on auto glass.

Post buffing clean up is usually just soap and water. I'd try a wet towel draped or otherwise fixed to the area, and kept wet for some hours. It should soften the compound.

Evoke appears to be buffing all their work, so you might ask them.


I've managed to get rubbing/polishing compound "sling" on my transparencies. Even with the slow-start buffer, it was easy to do. These little splatters have dried into tint hard bumps on the windscreen that do not scrape off easily with a fingernail and are still adherent after going over them with a wet microfiber towel and attacking them a little more aggressively with Plexus polish and with Novus polish No. 1.

I suppose I could attack this with Novus 3, 2 and 1, as in a complete restoration, but I was wondering if there is a safe solvent that might re-suspend this compound so it would wipe off as it would when freshly wet. Diesel fuel? Kerosene? Naphtha? I don't want to damage anything by a hasty shortcut.

Tips appreciated.
 
Thanks, Dan. I'll give that a try this morning. I have a BFR scheduled this evening and I'd hate to let the CFI see my windscreen all speckled with zits, especially since he's an RV-10 guy who had his plane professionally painted and didn't need the cut and buff. I'd hear lots of ribbing :D
 
I've managed to get rubbing/polishing compound "sling" on my transparencies. Even with the slow-start buffer, it was easy to do. These little splatters have dried into tint hard bumps on the windscreen that do not scrape off easily with a fingernail and are still adherent after going over them with a wet microfiber towel and attacking them a little more aggressively with Plexus polish and with Novus polish No. 1.

I suppose I could attack this with Novus 3, 2 and 1, as in a complete restoration, but I was wondering if there is a safe solvent that might re-suspend this compound so it would wipe off as it would when freshly wet. Diesel fuel? Kerosene? Naphtha? I don't want to damage anything by a hasty shortcut.

Tips appreciated.

I also learned that painful lesson the hard way. Within an hour or two it wipes right off with water. A day later, it is like an adhesive. Just don't understand how that happens. I have had good luck with mineral spirits or VM&P Naptha, though it seems you need to keep working that area to allow it to fully soak into the specks in order for them to release their bond. mineral spirits and kersosene are on the safe list for plexi, if I recall.

Larry
 
Last edited:
I did the barber shop hot towel treatment for 1/2 hour just now, followed by vigorous hand wiping with a microfiber rag. It sorta kinda works, as in the specks are disappearing little by little. If I rub one area continuously I can see individual specks start to vanish, which is a good sign.
 
Evoke appears to be buffing all their work, so you might ask them.

I saw that thread. I am shocked, shocked I tell you, to hear you insinuate that they can't get results that good straight out of the gun! :p

(It actually makes me feel better that they might have to buff some of their work, too. Misery, company, and all that).
 
Back
Top