smontanaro 

I strip paint from a lot of wood in support of my lovely wife's house projects. I use heat instead of chemicals. There's less mess, and after 30-odd years of it, I've gotten pretty good at getting the paint off without burning the wood.

So, I'm stripping a piece of molding this morning and it occurred to me that perhaps I could strip paint from a steel bike from using a heat gun. I can't see that the heat buildup would be high enough to damage the frame (certainly no worse than media blasting), especially if done with a modest amount of care. Aside from the convenient lack of proper scraper blades (which I could likely make or have made), what other problems would present themselves? Even if I could only get the main tubes done and had to resort to chemicals or blasting to do the lugs and other fiddly bits, I think I would still drastically reduce the use of nasty chemicals and metal-warping media blasting.

I don't think I've ever heard of someone using heat to strip paint on a bike, so I assume I must be missing something. Feedback appreciated.

thumpism 

Wouldn't hurt to try it, but make sure you begin with the heat gun on its lowest setting.

sloar 

I've used a heat gun and an old dull pocket knife. Worked ok, a little slow but not near as messy than using chemicals.

rhm

I saw this done once, about 35 years ago, one of the mechanics at the shop where I worked took all the paint off a frame using a torch. I'm not sure why he did it that way. It definitely worked, though it smelled awful. I can only speculate about damage to the steel or the brazing.

When I need to strip a frame, I start with a knife, then move to sand paper, then use chemical stripper for the tricky spots. I think the key is: use the tools that you're good at using. Sounds to me like you have the necessary touch with the heat gun, so why not?

Lascauxcaveman 

Certainly worth a try, I think I'll give it a shot myself, I have an old bent fork and heatgun to play with.

It's possible heat works so easily on wood partly because it's a different kind of paint and also the moisture in the wood, when heated up, helps repel and crack up whatever coatings are on it. You've probably already noticed that glossy top coats come up a lot easier than wood primers that are designed to penetrate into the wood.

Insidious C. 

Some powder coat shops will bake a frame in an oven until all that remains is bare metal. The heat gun should be safe, the challenge will be that heat will want to conduct in the tubing away from the small area you are working on with the heat gun. I say give it a try and post your results here.

nlerner

What could possibly go wrong?

b dub 

Smontanaro, I have a broken frame if you need something you can experiment with.

RosyRambler

Some years ago I stripped a lugged frame with a citrus stripper. It was in a soft paste form and I just brushed a thick coat of it on the frame and wrapped the frame tubes in plastic grocery shopping bags, left it overnight and the next day the paint easily came off with a paint scraper. The scraper was more to 'wipe' the paint off, no pressure was necessary. There were just a few areas that I had to reapply some stripper. I was pleasantly surprised how easy it was.

A heat gun seems like it would be a lot more time consuming and effort.

randyjawa 

I would not even consider heat to remove paint. One mistake and there goes the frame. Besides, there are so many cleaner and easier and safer ways to remove paint from a bicycle frame. Takes me between three and four hours to get to bare metal and without putting the frame (or me) in harm's way...

Trevtassie

Reckon heat wouldn't be that effective with enamel paint on old bikes. Wood , as the caveman says, is a different thing to steel, the heat releases moisture and oil from the substrate and this stops the paint from sticking. You could try the citrus type strippers, wrapped in cling film overnight or something like Peel-A-Way which is caustic based. Or look at getting the frame soda or sand blasted.

smontanaro 

@randyjawa What do you use?

Note that I'm not necessarily planning to do this, mostly just wondering if it's possible at this point. The alternatives don't seem all that friendly. I've used citrus-based strippers as well as more dangerous chemicals on wood before. Both leave you with a huge mess to clean up, not to mention the potential health risks of the more dangerous stuff. I know that media blasting will warp automotive sheet metal, which is much heavier than bike tubing.

I might take @b dub up on his broken frame suggestion, just to see if my crazy idea will work.

randyjawa 

This is how I usually remove paint. I prefer the rubber wheel on a 1/4" drill motor(don't go to fast and DO NOT use such a wheel on a high speed hand held mini grinder) coupled with some smaller scrapers, for detail work...



If stripping paint off of chrome, such as in the case of this all chrome Torpado, and I wish to preserve the chrome, I use chemical stripper, even though I hate doing so. I do not want to damage chrome with abrasion during the paint removal stage. Actually, I don't want to damage chrome at any time...

smontanaro 

@b dub was nice enough to drop off a wrecked Bianchi frame so I could experiment. A couple nights ago, I took a crack at the head tube. All I had handy to scrape with were the flat scrapers I was using for stripping wood. Here's the before (the red is a reflective sticker):



Here's the after, just the front of the head tube:



That was about six minutes of scraping with the heat gun and the edge of a flat scraper.

This morning, I was searching for something else out in the garage and came across an old circular gouge of my father's. He died in 1971, so it's a small miracle that I've managed to hang onto it all these years through multiple colleges, and raising three boys at various places around the country.



With my newfound tool, I spent a few minutes working on the top tube. Here's before doing one half of it (the bits of paint are klingons from scraping the other side):



Eight minutes later, after scraping and a little bit of sanding with a bit of crocus cloth I had laying about:



I don't think the metal gets too hot. The heat gun I have is a Milwaukee 750. The box says it has 500° and 750° settings. I always use the lower setting. It seems the technique has possibilities. I'll probably have to find gouges with different radii for the down tube and head tube. And I'll obviously need other techniques for the odd-shaped areas.

gugie 

Let's think about this logically. How hot does a steel frame get while brazing? Brass and bronze brazing alloys typically melt at temperatures above 1500F. Silver melts at around 1200.

So why would a 750 degree heat gun hurt a frame? Especially since this is actually the air temperature, and the metal tubing conducts heat away from the direct hot air as it acts as a fin?

I say use the high temp setting. Logic says it shouldn't hurt anything.

Use good ventilation, proper mask, etc.

BTW, the pictures/links are broken.

smontanaro 

I didn't think it would. In my experience stripping paint from wood, the low setting was plenty hot enough, however. I don't see any reason to run the heat gun hotter than necessary. Had the low setting not worked, I would have tried the high setting.

They work for me. I uploaded them to the server, then linked to the large version of the pictures, so it's not like I linked to a private URL. Is anyone else having trouble? If so, perhaps a moderator can take a look? (Wouldn't it be nice if @Moderator alerted them?)

jimmuller 

I see neither pics nor links.

Pompiere

I am not able to see the pictures either.

I have never tried using heat to strip paint from any surface, so I was a bit skeptical. I have a heat gun now, so I will have to give it a try on my next project.

smontanaro 

Okay, here's what I think happened. I did my usual tedious trick:

* insert an image, uploading from my local disk
* preview the post
* click the attached image icon to see the full image
* copy its URL (which will be on the server)
* use that URL to replace the [ ATTACH ] thing with and [ IMG ] thing

This generally to work for me, though leaves the little attachment icons at the bottom of the post. This time, the attachment icons are not there. My guess is they were deleted from the server. (I did not see them in my "Manage attachments" page.) I suspect the only reason the images displayed for me was that I had them cached in my browser.

I went back and uploaded all the images again, leaving them in their small state. Click to see the big picture. Can someone confirm that they are now visible?

@Moderator I noticed my Manage attachments page shows no images before 2015-08-07. My guess is that most of my uploaded images were deleted from the server.

RobbieTunes

Skip,

Simply because of your thread here, I am anticipating a heat gun. They have a 750/1000 at Walmart for about $30 on sale. I had no problem viewing the pics.
I can strip most frames with stripper, would like to do a better job. If my coater doesn't have to strip much, seems he does a much better job. (human nature factor?)

Brewsmith 

Ive stripped a frame down in a couple hours using a torch to heat the paint until brittle, then hitting it with a fine wire wheel. Works great, but is admittedly a bit dusty

Salamandrine 

Actually, temper is affected at temperature much lower than you would think. Cromoly is typically tempered at 4-500 degrees for an hour. Probably in most cases it's not going to matter much if the steel gets a tiny fractional amount softer (annealed). For an inexpensive bike, I wouldn't worry about it, but if it's some sort of high end frame, use chemical stripper. (where a respirator and do it outside!)

Prowler 

Jolly good discussion about the rating of the heater (makes no sense to me as my heater is rated in watts vs temperature) but someone is forgetting that what the heater 'can do' and what it will do are two entirely different things. Its hot air and it's impact on the steel tubing has much more to do with how far the nose of the heater is from the tube and how much and how fast you move that hot air. When I use mine its rare that I put the nose on the piece and hold it there. I can turn steel orange with mine but that takes time and focus. Normally I'm holding the heater well back and sweeping back and forth to warm a section of something, moving in bit by bit to get the temperature I want. Rarely just jam it in there and blast away.

It seems to me that the question is how warm do you you need to get the paint to soften and loosen up? I really wonder if that's anywhere close to the tempering range. You roast at turkey at around 325 and that pan will burn your hand good. OP: do you need to get the paint so hot that you cannot touch it? Would it burn you? That hot for a couple mils of paint?

gugie 

So how do you explain the much higher temperatures that the tubing sees during brazing?

I've used the chemical stripper approach, but it's tedius, messy, and nasty to clean up. Short of media blasting, I'm very tempted to try the heat gun method next time I strip a frame. I doubt if the metal actually gets anywhere near the same temp as the heat gun air. The higher setting would just make for a faster process, I would think.

unworthy1

OK so following the link this is :
"...a machine powered rotary wheel of some kind." How about a name or brand? I've used numerous wheels (sandpaper, wire, nylon fiber with "grit") and never seen one like this with "rubbery fingers"...what is it and do you need to add abrasive (powder) to use it?

BTW I HAVE used a heatgun (I own three) with scraper(s) to remove paint and varnishes on WOOD, sometimes depending on the job, but never on a bike frame. The idea with a heatgun is to SOFTEN the finish and follow with the scraper immediately, so that I sometimes use a gun with a scraper that fits right on the nozzle, which is very effective but you have to constantly clean off the hot gooey paint so heat-proof gloves are a MUST!