Unfinished Radiator?

WJK59

I just spent a few weekends stripping paint off of a 12-fin cast iron radiator. Pretty tedious work. I applied a couple of treatments of Ospho to convert any rust, and have it pretty much in raw, unfinished form. I had planned on priming and painting (w Rustoleum engine primer and white 600-degree high heat spray paint), but my wife now likes the look of the raw cast iron, even though it's a little uneven, and there's some very minor and relatively unnoticeable remnants of paint that I'd need to go at with a Dremel drill. That said, I'm slotted for knee surgery this morning, and had to get the very heavy unit back into the house and hooked up in its present condition, and to defer any paint finishing until the spring.
My question is, since I treated it with Ospho, should it be relatively OK to leave as-is, if desired, through the heating season, through the heating season, or even permanently, or should I absolutely figure on finishing it in the spring, either w linseed oil, high-heat spray clear coat (not sure it's quite pristine looking enough for that) or primer/cast iron enamel?

random12345

Any idea who the manufacturer is? Is this original to your house? When was your house built? There is embossed writing around the bottom tapping but I can't make it out from the picture. Is this used for steam or forced hot water? I like learning about these old radiators.

As for your question, no idea. Looks like Ospho is meant to be used before painting, not as a substitute. I think the paint you are considering is not appropriate. I assume you have steam? Any primer/paint you use is going to generate an atrocious stink for weeks...May not be a good time for that with your surgery.

Jamie Hall

The problem is that it is going to rust. Mybe not fast, but it will -- and maybe not evenly. It's lovely to look at though. Nice job! But I do not know of any clear coatings that will handle the temperature -- shellac tops out at 160F, and polyurethane varnishes at around 200.

On the other hand, you do not need high temperature paint -- which, as @random12345 noted will stink for weeks. I have had excellent success with steam radiators simply using a very good quality acrylic (I use Benjamin Moore Aura) paint without a primer. Little or no odour, and pretty much any colour you want.

hot_rod

Clear enamel should work. A customer of mine has a bunch of radiators sandblasted and clear powder coated. But those powder coat ovens run over 400F.

random12345

When I was looking into getting one of my Burnham rads refinished, US Boiler tech support told me not to go with powder coating because the joints would not be able to withstand the high temperature of the oven. Found a shop outside Boston that specialized in repainting rads, and he said the same thing. We went with him. Found another shop online and was told likewise, that she had seen powdercoating cause them to leak. We got ours primed and painted with Rustoleum Stops Rust metal primer and then the same brand Stops Rust protective enamel. It stank something awful for many weeks so we taped a thick plastic tarp from Home Depot onto the floor and walls around it and opened the window it was sitting under.

A more elegant solution would have been to go to a sheet metal fabricator and have them build a custom metal radiator cover with a round hole in the top cover. Make a cutout in the bottom of one side to make room for the steam feed. Place the box over the rad and tape all around where the box touches the floor, then buy a cheap flexible hot air duct, put it into the top hole and use a window duct vent to the outside. That way, you can still get a little heat into your living space while it's off-gassing to the outside, which for us lasted months.

https://www.lowes.com/pd/Deflecto-Aluminum-Flex-Duct-50ft/5005420613?cm_mmc=shp-_-c-_-prd-_-app-_-ggl-_-PLA_APP_174_Laundry-_-5005420613-_-online-_-0-_-0&ds_rl=1286981&ds_rl=1286890&gclid=EAIaIQobChMInvbz8aHO-gIVh9zICh1IhQMzEAQYAyABEgKUSPD_BwE&gclsrc=aw.ds

https://google.com/search?q=window+duct+vent+for+ac&rlz=1C1CHBF_enUS870US870&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiLgpW1oc76AhW9LFkFHXaaCHsQ_AUoAnoECAEQBA&biw=1536&bih=722&dpr=1.25#imgrc=xAZSuVxkvi119M

hot_rod

It depends on how the sections are assembled, push nipple or o rings. I test his after he had the coated, worried about leaks at the sections, all tested to 30 psi. But error on the safe side and find a paint or clear that works

I like the look of the bare iron also, clear coat would make it easier to dust them off.

random12345

I thought they all used push nipples. Steam rads have o rings? What are they made out of?

EdTheHeaterMan

@random12345 said:
A more elegant solution would have been to go to a sheet metal fabricator and have them build a custom metal radiator cover with a round hole in the top cover.

Great Idea, I believe the Louvre is thinking of getting a sheet metal cover for the Mona Lisa.

Would you prefer round circles or diamond shape screen to look thru?

random12345

EdTheHeaterMan said:

@random12345 said:
A more elegant solution would have been to go to a sheet metal fabricator and have them build a custom metal radiator cover with a round hole in the top cover.

Great Idea, I believe the Louvre is thinking of getting a sheet metal cover for the Mona Lisa.

Would you prefer round circles or diamond shape screen to look thru?

I should have added the word "temporary". After it has off-gassed for a few months, the cover gets put away until the next time another rad gets repainted.

WJK59

random12345 said:

Any idea who the manufacturer is? Is this original to your house? When was your house built? There is embossed writing around the bottom tapping but I can't make it out from the picture. Is this used for steam or forced hot water? I like learning about these old radiators.

As for your question, no idea. Looks like Ospho is meant to be used before painting, not as a substitute. I think the paint you are considering is not appropriate. I assume you have steam? Any primer/paint you use is going to generate an atrocious stink for weeks...May not be a good time for that with your surgery.

They're original, and manufactured by Detroit Radiator Co., although I'm not sure what year they were installed - the house was built in 1876. Yes, my intention was to treat them with Ospho prior to painting, but they took longer than anticipated and weather didn't cooperate, so I ran short on time. One-pipe steam system. I feel pretty confident about the high-temp engine enamel, but am not 100% sure I need to go that route at this point. It will be in the spring, anyway, as I'm not going to be disconnecting it again before the end of the heating system. And yep - not great timing with the surgery...

WJK59

Jamie Hall said:

The problem is that it is going to rust. Mybe not fast, but it will -- and maybe not evenly. It's lovely to look at though. Nice job! But I do not know of any clear coatings that will handle the temperature -- shellac tops out at 160F, and polyurethane varnishes at around 200.

On the other hand, you do not need high temperature paint -- which, as @random12345 noted will stink for weeks. I have had excellent success with steam radiators simply using a very good quality acrylic (I use Benjamin Moore Aura) paint without a primer. Little or no odour, and pretty much any colour you want.

I was hoping to avoid a brush-on finish, and to go the spray route, but that will be dependent upon the final color/finish, also. If it does start to rust (which was really the root of my question, as I'm not entirely sure it will, since it's been treated), I can always it it with another Ospho treatment in the spring. There are some clearcoat engine paints that I could apply in the non-heating season to address the burn-off smell, and some linseed oil-based paints and treatments (some spray/some brush-on) I may also look into, depending upon the final finish (if any different from today!)

WJK59

hot_rod said:

Clear enamel should work. A customer of mine has a bunch of radiators sandblasted and clear powder coated. But those powder coat ovens run over 400F.

Yeah, well, I initially thought $40 per fin for sandblasting and powdercoating was expensive - PLUS, having to get the radiator, which weighs a few hundred pounds, to the powdercoat shop sounded like an ordeal in and of itself. That said, in retrospect, given the amount of labor and materials I invested to get the radiator to this point, it's looking like a relative bargain.

WJK59

random12345 said:

When I was looking into getting one of my Burnham rads refinished, US Boiler tech support told me not to go with powder coating because the joints would not be able to withstand the high temperature of the oven. Found a shop outside Boston that specialized in repainting rads, and he said the same thing. We went with him. Found another shop online and was told likewise, that she had seen powdercoating cause them to leak. We got ours primed and painted with Rustoleum Stops Rust metal primer and then the same brand Stops Rust protective enamel. It stank something awful for many weeks so we taped a thick plastic tarp from Home Depot onto the floor and walls around it and opened the window it was sitting under.

A more elegant solution would have been to go to a sheet metal fabricator and have them build a custom metal radiator cover with a round hole in the top cover. Make a cutout in the bottom of one side to make room for the steam feed. Place the box over the rad and tape all around where the box touches the floor, then buy a cheap flexible hot air duct, put it into the top hole and use a window duct vent to the outside. That way, you can still get a little heat into your living space while it's off-gassing to the outside, which for us lasted months.

https://www.lowes.com/pd/Deflecto-Aluminum-Flex-Duct-50ft/5005420613?cm_mmc=shp-_-c-_-prd-_-app-_-ggl-_-PLA_APP_174_Laundry-_-5005420613-_-online-_-0-_-0&ds_rl=1286981&ds_rl=1286890&gclid=EAIaIQobChMInvbz8aHO-gIVh9zICh1IhQMzEAQYAyABEgKUSPD_BwE&gclsrc=aw.ds

https://google.com/search?q=window+duct+vent+for+ac&rlz=1C1CHBF_enUS870US870&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiLgpW1oc76AhW9LFkFHXaaCHsQ_AUoAnoECAEQBA&biw=1536&bih=722&dpr=1.25#imgrc=xAZSuVxkvi119M

Interesting counter-observation on the powder-coating. Thanks for that. My problem is that it's a steam radiator, that can get above 200 degrees, which is higher than the Rustoleum Stops-Rust products are rated for. Trust me - I contacted Rustoleum to inquire about which of their paints might work, and they really didn't have a good solution. Their "high-heat" paints, with the exception of some of the automotive engine paints, all require curing for a few hours at 350 degrees or above. Interestingly, Rustoleum does make a "radiator paint" that's sold in the UK, but not available in the US.

WJK59

EdTheHeaterMan said:

@random12345 said:
A more elegant solution would have been to go to a sheet metal fabricator and have them build a custom metal radiator cover with a round hole in the top cover.

Great Idea, I believe the Louvre is thinking of getting a sheet metal cover for the Mona Lisa.

Would you prefer round circles or diamond shape screen to look thru?

I have some painted units I'd consider buying or building nice wooden covers for - but I've got some radiused wall corners the some of the radiators are near that would end up with an awkward gap at the juncture of the radiator and walls - and I think a scribed top would look a bit odd. It's a heck of a lot of work to strip whatever kind of paint it was that was applied, which has been baked into a nasty hard putty over the years, but they ARE kind of beautiful when they're cleaned up!

WJK59

random12345 said:

EdTheHeaterMan said:

@random12345 said:
A more elegant solution would have been to go to a sheet metal fabricator and have them build a custom metal radiator cover with a round hole in the top cover.

Great Idea, I believe the Louvre is thinking of getting a sheet metal cover for the Mona Lisa.

Would you prefer round circles or diamond shape screen to look thru?

I should have added the word "temporary". After it has off-gassed for a few months, the cover gets put away until the next time another rad gets repainted.

Unless you vent that (along with most of the heat) to the outside, isn't that just venting the same smelly air into the room?

PC7060

WJK59 said:

Unless you vent that (along with most of the heat) to the outside, isn't that just venting the same smelly air into the room?

Covering the radiator reduces heat output so maybe less off gassing?

Jamie Hall

I'll say it again, since it's gotten lost in the fog: I give rusty radiators are thorough wire brushing -- in place -- and then paint them promptly with Benjamin Moore Aura, usually eggshell, in the colour which is needed. No stink. No heaving them around. No fancy priming. No fancy finishes in more or less arbitrary colours. Get the paint at the local paint store.

I have a number which I did that way 20 years ago (it was an earlier version of Aura, but same idea) and they are still rust free.

What's not to like? Keep it simple.

random12345

Jamie Hall said:

I'll say it again, since it's gotten lost in the fog: I give rusty radiators are thorough wire brushing -- in place -- and then paint them promptly with Benjamin Moore Aura, usually eggshell, in the colour which is needed. No stink. No heaving them around. No fancy priming. No fancy finishes in more or less arbitrary colours. Get the paint at the local paint store.

I have a number which I did that way 20 years ago (it was an earlier version of Aura, but same idea) and they are still rust free.

What's not to like? Keep it simple.

Maybe that's what we should have done...One of our rads didn't get used much and the valve was completely closed for many years. It had been brush painted with a thick coat of regular paint years ago. When we decided to start using it again, even after it had "cured" for all those years, it still stank so badly and for so long, that we decided to get it stripped and repainted by a pro. When it had been professionally refinished, it still stank afterwards, but because he spray painted it, the coating was a lot thinner and now it doesn't smell anymore. Also, Burnham told me that they recommended an oil-based enamel for their radiators. Would a sloppy painter using that Aura paint really not have any off-gassing problems at all? Also says that the max temperature is 100 F. Doesn't say anything about max substrate temp, only during application, but says it needs a primer.

https://media.benjaminmoore.com/WebServices/prod/assets/production/datasheets/TDS_0632/N632_TDS_US.pdf

A few of our rads were spray painted without primer. Now they are chipping.

Jamie Hall

I can only say what my experience has been. And it has been good. I will say for that maximum temperature -- they're right, but it applies to application, not, so far as I can make out, use. If it either the surface or the air is too warm when you apply the stuff, it starts to dry before it starts to cure, and won't cure properly, since it needs the water in the mix to cure.

The only time I've had chipping trouble have either been grease or oils left on the surface -- or, more often, sloppy work and gotten a coat too thick.

random12345

WJK59 said:

They're original, and manufactured by Detroit Radiator Co., although I'm not sure what year they were installed - the house was built in 1876. Yes, my intention was to treat them with Ospho prior to painting, but they took longer than anticipated and weather didn't cooperate, so I ran short on time. One-pipe steam system. I feel pretty confident about the high-temp engine enamel, but am not 100% sure I need to go that route at this point. It will be in the spring, anyway, as I'm not going to be disconnecting it again before the end of the heating system. And yep - not great timing with the surgery...

Interesting. Just learned that Detroit Radiator Co. was one of the predecessors of American Radiator Company. Looks similar to this: https://archive.org/details/idealfitterameri00amerrich/page/54/mode/2up

WJK59 said:

Interesting counter-observation on the powder-coating. Thanks for that. My problem is that it's a steam radiator, that can get above 200 degrees, which is higher than the Rustoleum Stops-Rust products are rated for. Trust me - I contacted Rustoleum to inquire about which of their paints might work, and they really didn't have a good solution. Their "high-heat" paints, with the exception of some of the automotive engine paints, all require curing for a few hours at 350 degrees or above. Interestingly, Rustoleum does make a "radiator paint" that's sold in the UK, but not available in the US.

Yes Rustoleum will tell you that, just as they told me. It's not true. There is nothing in that paint that cannot withstand 215 F. See the ingredient list below if you're considering this. We sent our rad to a shop that specialized in radiator refinishing. This was the paint he chose. It was professionally sandblasted and then spray painted with Stops-Rust primer and then the enamel semi-gloss. The high-heat temp paints are overkill, and are not designed for indoor use. I would avoid.

https://rustoleum.com/product-catalog/consumer-brands/stops-rust/protective-enamel-spray

https://rustoleum.com/product-catalog/consumer-brands/stops-rust/clean-metal-primer-spray

WJK59 said:

Unless you vent that (along with most of the heat) to the outside, isn't that just venting the same smelly air into the room?

Yes venting to the outside. The heat is lost, but no fumes.

Having said all of that, if @Jamie Hall says he has had a non-smelly experience with the acrylic paint he mentioned, then I would try that and forget the Rustoleum. Go with a very thin coat. If it stinks, then you will have to use the box and vent strategy or place a thick plastic sheet over it and tape that to the walls as we did.

WJK59

Thanks for all the feedback so far. Well, at this point, the unit is hooked up and heating nicely (no smell from the Ospho treatment, at least). I guess it will be a season-long experiment. In the meantime, would be interested in hearing back from anyone with any experience or insights about using a linseed oil treatment.

WJK59

random12345 said:

WJK59 said:

They're original, and manufactured by Detroit Radiator Co., although I'm not sure what year they were installed - the house was built in 1876. Yes, my intention was to treat them with Ospho prior to painting, but they took longer than anticipated and weather didn't cooperate, so I ran short on time. One-pipe steam system. I feel pretty confident about the high-temp engine enamel, but am not 100% sure I need to go that route at this point. It will be in the spring, anyway, as I'm not going to be disconnecting it again before the end of the heating system. And yep - not great timing with the surgery...

Interesting. Just learned that Detroit Radiator Co. was one of the predecessors of American Radiator Company. Looks similar to this: https://archive.org/details/idealfitterameri00amerrich/page/54/mode/2up

I have a number of American Radiator Co units out in my garage that I pulled out of a mansion that was going to be demolished years ago. I refinished one of those over the summer, also - but they all had a much thinner silver metallic applied finish, so much easier to strip and refinish. That was also before I discovered Ospho. That one I primed and painted with StopRust and an enamel topcoat - although haven't hooked it up yet.
Yes, it's not too dissimilar from the Rococco model you referenced - slightly less elaborate and with a somewhat different pattern, but clearly not too different.

random12345

WJK59 said:

I have a number of American Radiator Co units out in my garage that I pulled out of a mansion that was going to be demolished years ago. I refinished one of those over the summer, also - but they all had a much thinner silver metallic applied finish, so much easier to strip and refinish. That was also before I discovered Ospho. That one I primed and painted with StopRust and an enamel topcoat - although haven't hooked it up yet.
Yes, it's not too dissimilar from the Rococco model you referenced - slightly less elaborate and with a somewhat different pattern, but clearly not too different.

Radiators are interesting. I like looking through those old catalogs. Haven't been able to find one for yours though.

Be prepared for an epic stink once you hook it up.

WJK59

random12345 said:

WJK59 said:

Radiators are interesting. I like looking through those old catalogs. Haven't been able to find one for yours though.

Be prepared for an epic stink once you hook it up.

While I haven't hooked up the unit I painted, I DID hook up the 12-fin unfinished unit that I rust-treated. It was 34 degrees yesterday morning, and we've already run several heating cycles. No stink whatsoever.

random12345

Nice. Glad to hear it.