UV blocking primer

[Kevin Clay]

Hi Everyone,

I've got some bubbles and peeling in the Imron finish of my Varieze. I can't face the task of stripping and refinishing the whole plane right now, so I'm going to have to do spot repairs.  My main question is what UV blocking primer I can use that's available in quart sizes.  I've been looking for Dupont 131S but can't find it in a quart size (I just don't need a whole gallon).  The alternative that Spruce sells is waterborn and not recommended for wet sanding, which I'll want to do.  Anyone know what I can use under Imron?  Also, any advice on spot repairs to the finish would be welcome.

Thanks,

Kevin Clay 

[BruceHughes]

Kevin, Imron is VERY dangerous to work with.  Those professionals who apply it
use masks to remove the toxins.   Get a copy of the MSDS for any paint you
plan to apply and read the inhalation section and the cutaneous absorption
section.   I bet you will then have a professional do the repair.

Bruce Hughes   

[srothert]

Kevin,
Bruce is correct.  IMRON and the other equivalent brands of paint are very dangerous.  There have been a few deaths that have been written up because of "casual" protection.  I believe that one individual died within three days of applying the paint.  Professional painters use full body suits and full face masks, with pressurized air being delivered to the suit and mask, from an outside air source.  They also paint in a climate controlled paint booth that helps vents the fumes.

That being said, you should probably visit a reputable automotive paint supply shop and ask for their advice. The guys who work there are full of good information.  Some paint products are incompatible with other products, even when made by the same paint manufacturer.  The paint stores can probably also supply you with a Material Safety Data Sheet (MSDS) on the various products.  Most of their products are usually available in quarts.

Steve Rothert
Long-Ez N49SR
Albuquerque, NM

[av-mech]

Kevin,

I agree with the above posts but will additionally add an answer to your question.  It will be hard to find a high quality primer that is sold in quarts.  I would never say never but I have not been able to buy good quality primers in quart sizes ever.  Paints yes, primers no.  Don't ask why because I have no idea why they do that. 

For your repair, it's not too hard.  Using an appropriate tool like a plastic scraper or something similar, gently chip off the bubbles until you get it back to an edge where it is no longer bubbled or lifting.  start with some 180 sand paper and sand the edges where paint meets primer until you get something of a feathered edge, don't worry about sanding it super smooth yet.  you should also prep sand the painted area around the chipped edges for about 1 inch all around.  Tape off the area just a smidge beyond where you have sanded the paint.  Just use a good quality masking tape at this point.  Vacuum the area or at least blow it off and wipe down with Prep-Sol or some other similar wax and grease remover.  Do not use aggressive solvents because it may seep through pinholes in the laminate and melt your foam, depending on where the repair area is.  Next, Shoot primer predominatly in the area where the bubble was and only lightly where the paint is.  I use Corlar 2.1 primer, its an epoxy based primer that sands really well after curing.

[av-mech]

PT 2.

Other primers would be dupont 131S or WLS epoxy primer that Lancair sells.  None of these will be "cheap" but for the Corlar 2.1 (Dupont) runs about $100.00 for a kit.  The mix ratio is 2:1 but again for some stupid reason they only sell the kit in two gallon cans. (1 gallon part a and one gallon part b)  You end up throwing .5 gallon part b away.  I have complained about this but Dupont seems to not be interested in taking my calls......  There are certainly other good primers out there but I have had the best luck with these brands.  I have used the Corlar way more than the WLS and the 131S only in a pinch.  You must have the reducer for the Corlar so don't forget that, it has to be thinned for spraying. 

Shoot a couple of heavy coats on your repair area, give time between coats for each one to tack off.  No need to shoot so hard that you run it.  Give it overnight to cure.  After cure, remove tape and masking paper and set up some 320 on a sanding block.  Before sanding, spray a light coat of black lacquer spray bomb on the primered area, just a light dusting.  This is a guide coat so you can see whats happening while you sand.  give it about 15 min to dry and start blocking.  Don't use Krylon or similar for guide coat, when you buy your good primer at the paint shop ask them for a spray can of guide coat, they know what you need.  Block sand with the 320 just enough to level your primered area.

[av-mech]

PT. 3 

Once you are satisfied that you have either applied enough primer so that you don't need anymore to hide your edges, (or you need another coat), switch to wet/dry 400 on a block.  Start sanding with the 400 and keep it wet all the time.  I use a spray bottle with water in it and spray every 7-10 strokes to wash the grit away.  You should not have to do much sanding really to get this kind of repair done.  If you are only trying to fill in where paint was removed then I tend to stay away from any type of body filler, wether it be bondo or micro.  If it's deeper than the thickness of the paint layer than you may need a quick swipe of filler.  I would suggest that you take the time to use micro.  It sands well and is a better match with the base material in terms of thermal expeansion and contraction rates.  Bondo is a polyester based product and although tends to work, is not as good a match technically speaking.

When satisfied with your wet sanding, run a sheet of water across the repair area, when you remove the water source you will see what the surface is going to look like with paint on it.  The water sheen is a pretty good indicator of surface quality.  There are no "safe" paints but with todays technology almost any good quality ureathane based paint will adhere to your imron, so if you can get a good color match just use the brand that works best.  I recommend R&M "uno", for solid colors it's hard to beat.  Again, there are many great products, that's just one that works well for me.

[av-mech]

For painting, use a good charcoal filter mask at least.  If you can get a positive pressure air mask all the better.  I use both depending on the size of the job.  If just shooting a fairing or something small I usually just throw on the filter mask.  If shooting a fuselage or wing than it's full poopy suit and pressure mask.  For painting the repair area I tend to use more light coats rather than less heavy coats.  The location of the touch up will determine wether you need to mask it off or just feather it in.  I shoot using an HVLP gun set at about 30 psi and I usually feather in a touch up, wait for it to cure and come back with some 800 the 1000 wet/dry on a block.  Block the sprayed area and then come back with a buffer and some "Wizards turbo cut".  Be very careful with the buffer, it can generate a lot of localized heat if your not careful which can lead to delamination of the glass from the foam.  Generally, and I do mean generally these techniques work well for me in my shop.  Others will do things differently, others will use different products and that's all fine.  I only offer this advice as what works for me.  Good luck.

[BruceHughes]

I remember one fatality who used IMRON.   

I use PPG acrylic, spray outside, and use a good chemical filter.   All of my painting now is to do areas that would be completely covered by a sheet of paper or even a dollar bill.   I don't want to be in the same building with
IMRON.

The paint companies (the distributors) are REQUIRED BY FEDERAL LAW to furnish a MSDS for each product that they sell.   These may be found in a filing cabinet that is difficult to get to but INSIST that you want one.  They may not be happy but refuse to buy anything until you get the MSDS set.   If it is a good dealer, they will respect
the customer's wishes and hop to it.       It it is a poor dealer, it is easy to find another dealer on the internet.

When you read the MSDS you will be stunned at the level of danger of these products.  Be sure to read BOTH
the cutaneous exposure AND the inhalation exposure.

Bruce Hughes   

[Radioflyer]

Kevin, If it is not too late, you might want to investigate using Transtar 6134 Gray Epoxy primer (and 6144 activator). It is an easy to work with, 1:1 mix, zero induction time primer. Available in quart sizes for about $38 for the primer and $31 for the activator. It claims to be compatible with most paint systems. I don't know what its UV blocking properties are. I've used it a little bit on a metal plane, liked it, and intend to use it on my Long for some spot painting.

[dorr]

I had a Defiant with Featherfill as the primary fill material (Burt's original).  Found the bubbling got worse, like chasing gophers around the yard.  First I'd do 4" patches, all the way to the skin - but the bubbles would appear just outside the patches - then I tried 2' by 2' sections - after 3 years of filling, priming and repainting I had to strip the whole top of the plane (California dew/sunshine/dew cycle did the featherfill in at about 10 years... Replaced all filler with West and microballoons, the bubbling stopped.