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Gallery: Birth of a show bike, part two - Mosaic Bespoke Bicycles

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Aaron Barcheck founded Mosaic Bespoke Bicycles just five years ago but has already earned a solid reputation as one of the best titanium welders in the business

Aaron Barcheck founded Mosaic Bespoke Bicycles just five years ago but has already earned a solid reputation as one of the best titanium welders in the business (Image credit: Jonny Irick)
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It doesn't get much cleaner than this

It doesn't get much cleaner than this (Image credit: Jonny Irick)
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Kevin Batchelor buffs out a frame in preparation for final finishing

Kevin Batchelor buffs out a frame in preparation for final finishing (Image credit: Jonny Irick)
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Mosaic machines these 44mm-diameter titanium head tubes in house

Mosaic machines these 44mm-diameter titanium head tubes in house (Image credit: Jonny Irick)
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A good joint starts with a tight miter

A good joint starts with a tight miter (Image credit: Jonny Irick)
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Like many other builders, Mosaic Bespoke Bicycles uses Anvil frame jigs

Like many other builders, Mosaic Bespoke Bicycles uses Anvil frame jigs (Image credit: Jonny Irick)
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Barcheck has specific welder settings for pretty much every joint on the bike - and he's not about to share his secrets with just anyone

Barcheck has specific welder settings for pretty much every joint on the bike - and he's not about to share his secrets with just anyone (Image credit: Jonny Irick)
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It's one thing to make a weld structurally correct. Making it pretty is another thing entirely, particularly given such challenging geometry

It's one thing to make a weld structurally correct. Making it pretty is another thing entirely, particularly given such challenging geometry (Image credit: Jonny Irick)
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This pedal controls the flow of argon gas that's injected into the frame

This pedal controls the flow of argon gas that's injected into the frame (Image credit: Jonny Irick)
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Barcheck is fanatical about maintaining a clean welding environment. He's even careful when flipping his welding mask up and down so as not to send a draft of oxygen into the weld zone

Barcheck is fanatical about maintaining a clean welding environment. He's even careful when flipping his welding mask up and down so as not to send a draft of oxygen into the weld zone (Image credit: Jonny Irick)
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A wrap of aluminum foil creates a micro-environment around the dropout. Argon gas is still being injected at the bottom bracket and adding the foil here effectively holds the exiting argon gas a little longer to help prevent weld contamination

A wrap of aluminum foil creates a micro-environment around the dropout. Argon gas is still being injected at the bottom bracket and adding the foil here effectively holds the exiting argon gas a little longer to help prevent weld contamination (Image credit: Jonny Irick)
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Aaron Barcheck's tools of the trade

Aaron Barcheck's tools of the trade (Image credit: Jonny Irick)
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Barcheck uses a variety of heatsinks inside the bottom bracket and seat tube to help pull heat away from the weld zone

Barcheck uses a variety of heatsinks inside the bottom bracket and seat tube to help pull heat away from the weld zone (Image credit: Jonny Irick)
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This is how the dropout looks immediately after the second pass of welding. It's already virtually perfect as is but will look even better after it's buffed up. Again, note the almost complete lack of discolorization, which indicates a clean welding environment with little to no oxidation that can potentially cripple a frame later on

This is how the dropout looks immediately after the second pass of welding. It's already virtually perfect as is but will look even better after it's buffed up. Again, note the almost complete lack of discolorization, which indicates a clean welding environment with little to no oxidation that can potentially cripple a frame later on (Image credit: Jonny Irick)
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This is not a weld that's been dressed up for a photo. This was taken minutes after Barcheck had finished welding with no post-weld processing whatsoever. Note the complete lack of discoloration and the ultra-even weld beads. And see that little dot at the bottom? That's Barcheck's little 'signature' - sort of like how a mechanic will often crimp a cable end the same way

This is not a weld that's been dressed up for a photo. This was taken minutes after Barcheck had finished welding with no post-weld processing whatsoever. Note the complete lack of discoloration and the ultra-even weld beads. And see that little dot at the bottom? That's Barcheck's little 'signature' - sort of like how a mechanic will often crimp a cable end the same way (Image credit: Jonny Irick)
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Kevin Batchelor buffs up a freshly finished titanium frame with a strip of Scotch Brite

Kevin Batchelor buffs up a freshly finished titanium frame with a strip of Scotch Brite (Image credit: Jonny Irick)
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Barcheck periodically clips off the end of the welding rod, preferring to work with fresh material instead of stuff that's partially oxidized

Barcheck periodically clips off the end of the welding rod, preferring to work with fresh material instead of stuff that's partially oxidized (Image credit: Jonny Irick)
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Barcheck says dropouts are among the hardest things to weld given the complex geometry and dramatically different tube wall thicknesses between the seat stays and chain stays

Barcheck says dropouts are among the hardest things to weld given the complex geometry and dramatically different tube wall thicknesses between the seat stays and chain stays (Image credit: Jonny Irick)
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Aaron Barcheck welded his first titanium frame while a student at United Bicycle Institute under the tutelage of framebuilding legends Mike DeSalvo and Jim Kish

Aaron Barcheck welded his first titanium frame while a student at United Bicycle Institute under the tutelage of framebuilding legends Mike DeSalvo and Jim Kish (Image credit: Jonny Irick)
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Barcheck fusion welds the chain stay bridge in place before following up with the welding rod

Barcheck fusion welds the chain stay bridge in place before following up with the welding rod (Image credit: Jonny Irick)
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Now is not the time to strike up a conversation

Now is not the time to strike up a conversation (Image credit: Jonny Irick)
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Torch and rod in hand, Barcheck gets to work

Torch and rod in hand, Barcheck gets to work (Image credit: Jonny Irick)
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Aaron Barcheck checks his settings before starting to weld

Aaron Barcheck checks his settings before starting to weld (Image credit: Jonny Irick)
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Small bits to be welded or brazed on are sorted in plastic bins

Small bits to be welded or brazed on are sorted in plastic bins (Image credit: Jonny Irick)
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Mosaic can make you a custom stem, too

Mosaic can make you a custom stem, too (Image credit: Jonny Irick)
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Mosaic uses welding and brazing rods of various materials and sizes depending on the frame material and joint

Mosaic uses welding and brazing rods of various materials and sizes depending on the frame material and joint (Image credit: Jonny Irick)
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It's critical when welding titanium that it be done in an inert environment. Otherwise, the weld region can become oxidized and brittle, leading to possible failures down the road. In this case, argon gas is injected down by the bottom bracket and most of the other open ports on the frame are sealed off with tape or aluminum foil

It's critical when welding titanium that it be done in an inert environment. Otherwise, the weld region can become oxidized and brittle, leading to possible failures down the road. In this case, argon gas is injected down by the bottom bracket and most of the other open ports on the frame are sealed off with tape or aluminum foil (Image credit: Jonny Irick)
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Barcheck starts by first fusion welding the joints so that the tubes are securely connected and stable. He then does a second pass with welding rod to fill in the joint

Barcheck starts by first fusion welding the joints so that the tubes are securely connected and stable. He then does a second pass with welding rod to fill in the joint (Image credit: Jonny Irick)
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We shadowed Mosaic Bespoke Bicycles founder Aaron Barcheck as he welded together this titanium road bike

We shadowed Mosaic Bespoke Bicycles founder Aaron Barcheck as he welded together this titanium road bike (Image credit: Jonny Irick)
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Staring directly at a weld job in progress even for a moment can cause serious eye damage unless proper protection is used

Staring directly at a weld job in progress even for a moment can cause serious eye damage unless proper protection is used (Image credit: Jonny Irick)
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Barcheck pauses every few seconds but keeps the argon gas flowing. This allows some of the residual heat to dissipate while still preventing the hot metal from oxidizing

Barcheck pauses every few seconds but keeps the argon gas flowing. This allows some of the residual heat to dissipate while still preventing the hot metal from oxidizing (Image credit: Jonny Irick)
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Art in progress

Art in progress (Image credit: Jonny Irick)
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Barcheck alters the settings on his TIG welded depending on the material and joint. The exact settings are a closely guarded secret that he's figured out after years of trial and error

Barcheck alters the settings on his TIG welded depending on the material and joint. The exact settings are a closely guarded secret that he's figured out after years of trial and error (Image credit: Jonny Irick)
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It's always the details that matter. The brake housing is internally routed through the top tube but it's also fully guided to ease maintenance

It's always the details that matter. The brake housing is internally routed through the top tube but it's also fully guided to ease maintenance (Image credit: Jonny Irick)
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It's no small thing to be able to do such fine, precise work in these tight confines

It's no small thing to be able to do such fine, precise work in these tight confines (Image credit: Jonny Irick)
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Ever wonder what a welder sees through the mask? Here you go

Ever wonder what a welder sees through the mask? Here you go (Image credit: Jonny Irick)
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Cast aside the idea that welders can't drink coffee and still produce a nice, even bead

Cast aside the idea that welders can't drink coffee and still produce a nice, even bead (Image credit: Jonny Irick)
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Steady as she goes…

Steady as she goes… (Image credit: Jonny Irick)
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Barcheck builds every titanium frame with double-pass welds. The joints between the bottom bracket shell and the seat tube and down tube are fusion welded to start - meaning they're joined using only the welding torch. Barcheck does a second pass later using welding rod to reinforce the area, as seen in the joint between the seat tube and down tube

Barcheck builds every titanium frame with double-pass welds. The joints between the bottom bracket shell and the seat tube and down tube are fusion welded to start - meaning they're joined using only the welding torch. Barcheck does a second pass later using welding rod to reinforce the area, as seen in the joint between the seat tube and down tube (Image credit: Jonny Irick)
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This fixture ensures proper alignment when welding disc brake tabs

This fixture ensures proper alignment when welding disc brake tabs (Image credit: Jonny Irick)

This article originally published on BikeRadar

Things continue to hum along at Mosaic Bespoke Bicycles with all but one of the frames for next month's North American Handmade Bicycle Show either fully built, at paint, or awaiting just a few details. For Part Two of this series, we shadowed company founder Aaron Barcheck as he welded up a titanium frame and discussed what makes for a good, or bad, titanium weld – and what to look for when shopping for a custom TIG-welded custom bike of your own.

After carefully mitering the tubes and setting everything up in a burly Anvil frame jig – the de facto standard for the handbuilt industry – Barcheck starts with a full fusion weld that uses only the welding torch to join the tubes together. According to Barcheck, this helps ensure full weld penetration for a reliable joint and also provides a more even foundation for laying down the subsequent beads.

Welding rods are used for the second pass, creating that distinctive 'stack of dimes' look that's so coveted with TIG-welded titanium frames.

None of this differs too drastically from the procedure other builders may employ although the manner in which Barcheck goes about it seems particularly stringent. He's militant about preventing contamination and minimizing the damaging effects of heat. Titanium oxidizes when welded in the presence of atmospheric oxygen, which can make the surrounding area brittle and prone to eventual cracking, while excessive heat can burn away too much material, leaving a thin spot in a high-stress area.

To prevent contamination, Barcheck uses a constant flow of inert argon gas that's injected through the bottom bracket shell. Breather holes in the frame are selectively sealed off to create an even and thorough flow of gas through the frame (thus minimizing any residual oxygen that might be lurking in internal crevices and pockets) and there's also a flow of gas coming through the welding torch tip so as to sandwich the work area in 'clean' air.

Barcheck is even careful about how he flips his welding mask up and down so as to not inadvertently send a draft of dirty air toward a still-hot weld area.

Meanwhile, excessive heat buildup is prevented by the generous use of internal heatsinks, plus specific welder settings and welding rod gauges for nearly every frame joint and tube wall thickness combination. Barcheck also pauses after every few seconds of welding (but leaves the gas flow on in the torch), allowing heat to dissipate.

Barcheck says he's also refined his welding order over the years, not only working from rear to front on each and every frame but also following a very specific sequence on each weld. Mosaic just hired a new welder (stolen away from Moots) and it's only recently that Barcheck wrote the sequence down. Up until then it was a secret hidden away in his head and while we photographed both the sequence and the welder settings, we unfortunately can't share either of them.

We stood watch as Barcheck finished up one of his frames for NAHBS and even with no post-weld finish work whatsoever, the results were astonishingly clean and even with no discoloration to speak of.

Riders looking at buying a custom titanium frame – or even one that's more mass produced – typically won't have the benefit of standing over the builder's shoulder to observe their work, though. It's easy to look at a finished titanium TIG weld and comment on its quality based on how even and tidy the beads are.

However, that judgment literally only scratches the surface of how good that weld actually is. Underlying issues such as poor tube fusion and sloppy miters can cripple a frame down the road and even the telltale rainbow discoloration of a contaminated weld can often be buffed off, leaving customers none the wiser. According to Barcheck, one of the only externally visible signs of a poor weld is one that's undercut – meaning the weld area is actually thinner than the surrounding tube walls instead of being a clean and even fillet.

"Usually when a weld is finished, you can't see what goes into it aside from if it's aesthetically pleasing and maybe that it's not undercut," Barcheck said. "Beyond that, once it's in your media blaster and finish it off, it's hard to tell what it looks like."

"Structurally, there are a few things that go into making a good weld," he continued. "One would be a clean weld with correct back purge and top purge of argon on the frame. Specifically in regards to titanium, if it oxidizes at all, it drops in tensile strength and it drops in yield strength. A dirty weld is not a strong weld. It's going to break at some point."

"Secondly, a non-undercut frame makes for really structurally sound weld. So if you have any changes in wall thickness from one tube to the other that would be thinner than what they should be, you could have a stress riser that might present itself down the road."

Barcheck says anyone looking to purchase a titanium frame – from Mosaic or elsewhere – should do their research on the builder.

"To me, what I would tell people is that it's more about the experience of the welder themselves and to find out if their processes are right, if they're keeping consistent from frame to frame, what type of machine they're using to produce the welds. There's no simple answer."

We've got one more visit to Mosaic scheduled where we're finally get to see some of the finished projects that will eventually make their way over to NAHBS. Stay tuned.

This year's North American Handmade Bicycle Show will take place March 14-16 at the Charlotte Convention Center in Charlotte, North Carolina. Tickets are available for $8-18 per day or $50 for a three-day pass. Attendees can register on the official show website.