painting small steel frame damages

On Fri, 5 May 2017 11:49:26 -0700 (PDT),
wrote:

I can't really argue with you, Gene, except for the problem of masking after the sandblasting. It seems that inevitably the powder coat guy doesn't mask something that should have been masked (and then you have to remove the overspray; can be very tedious) or he masks something that shouldn't have been masked, and then it looks like hell. I like to do my own masking job.

I use bolts for all threaded holes, an old seat post for the seat tube
and discuss masking the B.B. and head tube openings, after the acid
dip, with the guy doing the coating. To date I've had no problems.

Overall, I haven't found powder coat to be that much more durable than single-stage urethane enamel. They each have their strong points. Yes, powder coat has a lot more surface hardness, but how hard a paint do you really need on a bike? Whereas urethane is more flexible and therefore doesn't tend to crack as much. A fortiori because I'm spraying the low-VOC California product and find it to be a very good paint giving excellent results.

On Fri, 05 May 2017 23:04:10 +0200, Emanuel Berg
wrote:

Almost any city has locations that will
sandblast and powdercoat a frame and fork.
This procedure is dirt cheap and the finish
extremely long lasting if not the height of
glossy finishes.

Ha ha, if I went to an establishment which you
describe with some of my frames they would
probably be stunned. Also, it would require me
to strip the bike. No, what I'm talking about
is a quick DIY fix. That said, the result is
not that bad. But please continue your
discussion of any methods to paint or re-paint
a bike, it doesn't bother me

The first frame and fork I took to the shop I use now, the "head
Office Girl" walked me back to the guy that actually did the work and
we had a discussion about what to do and not do. Since that first
frame the only thing we've discussed was when I wanted a two color
frame, where to mask it.

Radey Shouman wrote:

RGB is an additive color model, which is
appropriate for computer monitors. For paints
a subtractive color model is more useful.

Yeah, how does it really work?

If you use the color wheel, and the color you
wish is between color A and color B, but two
thirds from color A and only one third from
color B, does that mean you should mix one
third A and two thirds B to get it?

--
underground experts united
http://user.it.uu.se/~embe8573

add a small amount z to a small test volume of x ... 'measure' both volumes

when close try a volume for a small out of sight chip paint let dry

Both dry and larger volumes will skew the results

visit the paint Store fir a demo

On Friday, May 5, 2017 at 2:04:14 PM UTC-7, Emanuel Berg wrote:
Almost any city has locations that will
sandblast and powdercoat a frame and fork.
This procedure is dirt cheap and the finish
extremely long lasting if not the height of
glossy finishes.

Ha ha, if I went to an establishment which you
describe with some of my frames they would
probably be stunned. Also, it would require me
to strip the bike. No, what I'm talking about
is a quick DIY fix. That said, the result is
not that bad. But please continue your
discussion of any methods to paint or re-paint
a bike, it doesn't bother me

--
underground experts united
http://user.it.uu.se/~embe8573

Too bad I can't download pictures of some examples.

On Friday, May 5, 2017 at 6:44:59 PM UTC-7, John B Slocomb wrote:
On Fri, 5 May 2017 07:42:41 -0700 (PDT), wrote:

On Thursday, May 4, 2017 at 5:52:15 PM UTC-7, wrote:
Emmanuel, I'm afraid I am not big on repairing chips in a frame's paint. When the bike gets too chipped and has too many rust spots to suit me, I strip the components off the frame, sandblast it and paint it with single-stage automotive paint. Although 2-stage (clear coat) jobs are popular these days, I think clear coat would look obviously inauthentic. IMHO, single stage paint more closely duplicates the original finish.

You need a fairly good-sized air compressor to run a sandblaster. I use a Campbell Hausfeld 2-stage model that delivers about 18 SCFM and has an 80-gallon air tank. Just about any portable, pressure-fed sandblaster will do the job. Avoid siphon-fed blasters.

Almost any city has locations that will sandblast and powdercoat a frame and fork. This procedure is dirt cheap and the finish extremely long lasting if not the height of glossy finishes.

The shop I use does a two coat powder coating with "clear coat" as the
second layer. It does produce a fairly shiny coating although not as
glossy as "22 coats of hand rubbed lacquer".

I live one mile away from CycleArt. I dropped in and asked what he wanted for a paint job and he said $1200 with decals and a minimum of two months lead. The powder coat complete was $50 the next day.

That's pretty funny - we have an entire string of having to touch up scratches on bicycle paint and you ask "how hard a paint do you really need on a bike".

Apologies if I'm hijacking the thread, Gene, but I don't think that paint hardness and scratch/chip resistance are the same thing. For example, early Dupont Imron paint was very hard but chipped easily.

If anybody knows more about paint than I do, feel free to correct me.

On 5/5/2017 10:31 PM, wrote:
On Friday, May 5, 2017 at 6:44:59 PM UTC-7, John B Slocomb wrote:
On Fri, 5 May 2017 07:42:41 -0700 (PDT), wrote:

On Thursday, May 4, 2017 at 5:52:15 PM UTC-7, wrote:
Emmanuel, I'm afraid I am not big on repairing chips in a frame's paint. When the bike gets too chipped and has too many rust spots to suit me, I strip the components off the frame, sandblast it and paint it with single-stage automotive paint. Although 2-stage (clear coat) jobs are popular these days, I think clear coat would look obviously inauthentic. IMHO, single stage paint more closely duplicates the original finish.

You need a fairly good-sized air compressor to run a sandblaster. I use a Campbell Hausfeld 2-stage model that delivers about 18 SCFM and has an 80-gallon air tank. Just about any portable, pressure-fed sandblaster will do the job. Avoid siphon-fed blasters.

Almost any city has locations that will sandblast and powdercoat a frame and fork. This procedure is dirt cheap and the finish extremely long lasting if not the height of glossy finishes.

The shop I use does a two coat powder coating with "clear coat" as the
second layer. It does produce a fairly shiny coating although not as
glossy as "22 coats of hand rubbed lacquer".

I live one mile away from CycleArt. I dropped in and asked what he wanted for a paint job and he said $1200 with decals and a minimum of two months lead. The powder coat complete was $50 the next day.

That's pretty interesting. About ten years ago, I welded up some nice
ornamental railings for our indoor stairs and outdoor balcony. I looked
into powder coating, and while I don't remember the price, I decided it
was exorbitant. It was much, much higher than $50!


--
- Frank Krygowski

On Fri, 5 May 2017 12:27:11 -0700 (PDT), wrote:

On Friday, May 5, 2017 at 11:49:28 AM UTC-7, wrote:
I can't really argue with you, Gene, except for the problem of masking after the sandblasting. It seems that inevitably the powder coat guy doesn't mask something that should have been masked (and then you have to remove the overspray; can be very tedious) or he masks something that shouldn't have been masked, and then it looks like hell. I like to do my own masking job.

Overall, I haven't found powder coat to be that much more durable than single-stage urethane enamel. They each have their strong points. Yes, powder coat has a lot more surface hardness, but how hard a paint do you really need on a bike? Whereas urethane is more flexible and therefore doesn't tend to crack as much. A fortiori because I'm spraying the low-VOC California product and find it to be a very good paint giving excellent results.

That's pretty funny - we have an entire string of having to touch up scratches on bicycle paint and you ask "how hard a paint do you really need on a bike".

And the point where by Colnago B-stay enters the frame carrier the urethane paint cracked all around it because of the movement between the B-stand and the frame and you say "urethane is more flexible and therefore doesn't tend to crack as much".

Obviously our experiences are exactly opposite.
Paint thatb is too "hard" cracks and chips. What you need is paint
that is "tough". "tough" and "hard" are not the same, and although not
mutually exclusive, are not GENERALLY found in the same paint.

On Fri, 05 May 2017 21:34:40 -0400, Radey Shouman
wrote:

Emanuel Berg writes:

Frank Krygowski wrote:

Yes, something like that. For example, many
people don't know that adding a bit of blue
to a bright orange will tone down its
brightness, muting it a bit toward brown.
I had that problem with one frame I was
touching up.

I know the RGB color model of computers!
Here are the colors I use in a Linux virtual
terminal, the teletypewriters (ttys):

normal bright
bk r g y bl m c w bk r g y bl m c w
r 0 255 0 190 100 175 0 150 90 255 0 255 125 235 90 210
g 0 50 150 190 100 100 180 150 90 75 180 127 125 75 255 180
b 0 50 0 0 255 0 180 150 90 75 0 0 255 235 255 140

With a brush and a bunch of color cans, it
should be much harder to get the color one
desires, than just mixing red, green, and
blue...

RGB is an additive color model, which is appropriate for computer
monitors. For paints a subtractive color model is more useful.

See for example http://www.worqx.com/color/color_systems.htm
Cyan, Magenta, Yellow and Black