Repainting over glossy paint.

[Chuckanut]

I have a some stair handrails that I need to repaint. They were painted years ago with a high gloss paint, and the gloss has held out very well.

I have been advised to sand all the gloss off the paint, but others have said its only necessary to scratch the surface of the gloss

Since I am radically changing color, I will probably prime then paint the hand rails after sanding them. Is one primer better than others for use on glossy surfaces? Sanded or unsanded?

Thanks.

 

[Senator]

Spray it with an oil based primer, like Binz or the Sherwin Williams spray primer. A couple of spray cans should be enough. You do not have to cover it completely, just enough to get a surface for the top coat to 'grab' on to. You can just use a light coat.

 

[samclem]

I would give it roughing up with some 120 grit sandpaper--no need to remove it, just enough to give the primer a grip. Then I'd do what Senator suggested. Zinnser BIN primer works very well. It stinks a bit, though. It might work fine on its own, but the sanding only takes a minute and a handrail is a demanding spot.

 

[Chuckanut]

A neighbor mentioned an alcohol based primer that was supposed to stick to anything. Anybody heard of that. His only warning was to have lots of ventilation and don't' breath to deeply.

Edit to add: OK, I see that the Zinsser BIN product is just that an alcohol based shellac primer. They seem to think it will stick to just about anything including glossy paint.

 

[Peter]

Before applying primer, I would clean the surface thoroughly with TSP, or TSP substitute.

 

[photoguy]

I think some of the zinnser primers say not to use tsp.

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[ERhoosier]

Clean, sand lightly, prime, and paint. No need to completely remove the old paint unless it is deteriorating (cracking, peeling, etc.).

 

[ERD50]

I think some of the zinnser primers say not to use tsp.

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I wonder why, but the horse says so, so I'd listen:

http://www.rustoleum.com/~/media/Di...c-Base Primer Ultimate Stain Blocker TDS.ashx

bold mine

Surfaces should be clean, dry, sound and free of dust, dirt, excessive chalky material, grime, grease, oil, wax, mildew, wallpaper adhesive, or any contamination that may interfere with adhesion.

If unsure of cleanliness, always wash surface with household ammonia and water solution, appropriate cleaning solution or solvent (do not use TSP as a cleaner). Remove any peeling and/or unsound coatings. Sand any remaining paint film edges smooth with the surface.

I would think any handrail would have oils/dirt from hands, so I'd do the ammonia routine. I would think sanding would be a good thing, but apparently not required ( I think they are talking about sanding down any drip lines? paint film edges? is that the edge of a painted/non-painted area?).

-ERD50

 

[Walt34]

(is that the edge of a painted/non-painted area?).-ERD50

Either that or where the paint has peeled away leaving other paint with hopefully good adhesion in place.

 

[ERD50]

Either that or where the paint has peeled away leaving other paint with hopefully good adhesion in place.

Yes, that makes sense - thanks. -ERD50

 

[-Jackson-]

You would not use TSP with an oil-based paint because TSP is a caustic (alkaline) (why it's good for degreasing). Oil-based paints react with alkaline surfaces to form a soap-like substance that interferes with adhesion. It is the same reason why oil-based paints are not used on concrete (because concrete, especially new concrete, has a pretty high pH).

This article explains it pretty well:
http://www.keimpaints.co.uk/fileadmin/uk/pdf/Paint_Saponification.pdf

 

[photoguy]

You would not use TSP with an oil-based paint because TSP is a caustic (alkaline) (why it's good for degreasing).

I think there must be something else going on as well because zinsser recommends against TSP even for the water based primers (e.g. Zinsser 123).

Searching around on google, it seems like people are saying TSP might leave a residue. But in that case, wouldn't a warning to rinse off the TSP suffice?

Maybe this is just extra-boiler plate left over from the oil based instructions that they just copied over.

 

[-Jackson-]

I think there must be something else going on as well because zinsser recommends against TSP even for the water based primers (e.g. Zinsser 123).

Searching around on google, it seems like people are saying TSP might leave a residue. But in that case, wouldn't a warning to rinse off the TSP suffice?

Maybe this is just extra-boiler plate left over from the oil based instructions that they just copied over.

Not necessarily left over. Many coatings are effected by extreme pH. It is particularly harmful to oil-based paints because of the reaction of the oils to the alkali. It can certainly be detrimental to other types of coatings.


You're right that rinsing the TSP from the surface and bringing the pH down to a neutral level would be the right way to go. However, using a different cleaner/degreaser would prevent the possibility altogether. If possible, I would recommend cleaning with the type of solvent that makes up the paint vehicle. For an oil-based paint that might be an alcohol. For an epoxy its probably acetone, MEK or similar.

Whatever is used should be thoroughly rinsed from the surface and/or allowed to evaporate (in the case of the volatile solvents) prior to painting. Closely following the manufacturer's recommendations generally gives the best results.

As for the sanding question, completely deglossing the surface is probably the best course. I can't add much about the primer. Most of my experience is with industrial coatings like tank linings, structrual steel coatings, and concrete containments. I don't have much experience with wood. I would say the primer should be as recommended by the top-coat manufacturer. I perfer to stay with the same brand for the whole system. The primer should be compatible with the top coat, and using the primer recommended by the manufacturer assures that. For example, you would probably not overcoat an acrylic latex with an alkyd (oil-based) paint.

 

[photoguy]

Thanks Jackson

 

[Peter]

I guess I was the one that brought up the TSP question. I did say "TSP or TSP substitute", and I must confess that all I've ever used is the substitute. The bottle does say "leaves no residue" so I wonder if the warnings about TSP would apply as well to the substitute?

I've never had any problem using it, but of course that doesn't prove anything!

Anyway, thanks to all for pointing out the issue.

 

[Chuckanut]

I did lightly sand the surface so the gloss is scratched all over and gone in a few places. I then brushed on a coat of the BIN primer.

My goodness, that stuff sticks! Unlike latex paints and even some oil based paints which I can wash off my hands, this stuff will be on my skin until the top layer of skin wears off. That's a small price to pay for a good surface to that my final coat(s) of paint will stick to.

After Father's Day is over, I will put on my first coat and then a second coat if necessary.