You're staring at a bead that looks like a burned garden hose. The machine's dialed in, the argon's flowing, and the amperage matches the material. Yet TIG welds look bad even with correct settings.
That's because "correct settings" is only the starting line, not the finish.
In our research, we've seen this exact frustration across countless shop floors and garage forums. The American Welding Society notes that proper shielding gas flow is typically 15 to 20 cubic feet per hour, but as of 2026, even that baseline fails when something else goes off the rails. The real culprits hide in prep, torch angle, and reading the puddle.
Let's walk through what's actually going on.
Quick Answer
TIG welds look bad even with correct settings when contamination, technique, or gas coverage interferes. Clean the metal thoroughly. Check tungsten condition.
Verify torch angle and arc length. Adjust gas flow for drafts. Inspect discoloration to identify the specific issue.
Settings don't fix what's happening at the workpiece surface.
The Ugly Weld Mystery: Why Settings Aren't Everything
Every welder has been there. You set the machine exactly per the chart. The base metal is the right thickness, the filler rod matches the alloy, and your posture is steady.
The weld still comes out grey, rough, or sooty.
Here's the uncomfortable truth: TIG is a process of tiny variables. The dials control the arc, but the arc meets a surface that's dirty, a gas stream that's turbulent, or a tungsten tip that's contaminated. In our experience, most "ugly" TIG welds are not a machine problem.
They're a human and environment problem.
Think of it like baking. A perfect oven temperature doesn't matter if the dough is wet or the pan is greasy. Similarly, your amperage and gas settings only matter when everything around them is right.
The first step to fixing ugly welds is accepting that the settings are rarely the whole story.
So where do you look? Start by reading the bead itself. The weld's color, texture, and shape give you a direct diagnostic of what went wrong.
The rest of this guide breaks down each visual clue and what it means.
How to Read a Bad TIG Bead Like a Pro
A good TIG bead looks like a neat stack of coins, evenly spaced ripples with clean, shiny edges. Anything less than that is telling you something.
Let's break down the basic visual clues:
- Straw to dark blue color: Too much heat or insufficient gas coverage.
- Grey or black powdery soot: Usually contamination or oxygen in the gas stream.
- Pitting or tiny holes: Porosity from moisture, dirt, or a short post-flow.
- Rough, irregular ripples: Unsteady torch hand or filler rod dabbing too far.
- Undercut along the edges: Too much heat or a torch angle that's too steep.
The trick is to diagnose one clue at a time. For example, if the weld is shiny on the surface but grey right at the edge, the heat-affected zone is getting too hot between passes. That tells you to lower your amperage or speed up.
If the weld has a dusty black layer that wipes off on your glove, that's carbon. It usually means your shielding gas didn't fully cover the cooling weld. Could be low gas flow, a draft, or a loose connection in the gas line.
Best way to read a bead? Brace yourself and watch the puddle. The puddle's behavior matters more than the finished bead.
A puddle that looks syrupy and wets out smoothly will produce a clean weld. A puddle that spikes, boils, or flattens too much creates defects.
Discoloration and Heat Tint: The Color Chart Unlocks the Clue
Heat tint is your free diagnostic tool. Stainless steel and titanium change color based on temperature exposure and gas coverage. On aluminum, the color tells you about cleaning action and heat input.
Here's a practical reference table for stainless steel:
| Color | Indication |
|---|---|
| Bright silver / shiny | Excellent gas coverage, correct heat |
| Straw / light gold | Acceptable, slightly high heat or short post-flow |
| Dark blue / purple | Too much heat or gas coverage lost too early |
| Grey / dull | Significant overheating, risk of corrosion |
| Black / sugary | Severe contamination of gas or base metal |
On aluminum, the colors run differently. A bright, silver, almost frosted appearance after the brush is normal. A dull white layer means overheating.
A grey, sooty streak means your AC balance or shielding is off.
Aggregate reviews from professional welders confirm that post-flow time is often the culprit for unwanted discoloration. When the weld is still cherry red after you lift the torch, it needs argon coverage. A post-flow of 5 to 10 seconds is the standard.
If you stop the gas too quickly, oxygen rushes in and tints the weld.
If you see brown or gray discoloration on stainless, that's a problem. It suggests the shielding gas didn't protect the hot metal during cooling. Sometimes raising your gas flow helps.
Sometimes you need a larger cup or a gas lens. This is where proper equipment pays off.
Soot and Carbon Buildup: It's Not the Amperage, It's the Air
Soot on a TIG weld is the most annoying problem because it looks like your machine is burning something. Usually, it's not the arc at all.
Black, powdery soot around the weld suggests that the shielding gas is being pulled away or contaminated. Common causes:
- Drafts and fans: Even a gentle breeze can disrupt the gas blanket. Move your work away from open doors, vents, or shop fans.
- High gas flow: Believe it or not, too much argon creates turbulence. That pulls air in instead of keeping it out. Stay within 15 to 20 CFH unless you have a large cup.
- Oil or solvent residue: Many degreasers leave microscopic films. Acetone works best. Use a clean rag, then a dedicated stainless wire brush.
- Moisture in the hose: Water vapor from a previous gas cylinder or a leak breaks down in the arc, creating hydrogen and carbon.
Check your gas lens. A standard collet can work, but a gas lens provides a more laminar, even flow. That's especially useful on stainless and aluminum.
If you're seeing soot, your gas is either too turbulent or too weak.
Also, look at your filler rod. If you've handled it with oily gloves, the rod introduces contamination directly into the puddle. That produces carbon streaks and porosity.
Store filler rods cleanly and wipe them before use.
Tungsten Point Problems: Balling, Wandering, and Contamination
The tungsten electrode is the beating heart of TIG. If it's wrong, your weld will misbehave no matter the settings. Check these three things before you change anything else.
Balling at the tip: This happens when you're using pure tungsten on DC, or the amperage is too high for the tungsten diameter. A balled tip creates an unstable arc that wanders, and that gives you a wandering bead. Fix: switch to a rare-earth tungsten like lanthanated or ceriated, and grind to a taper.
Wandering arc: If the arc looks like it's dancing side to side, the tungsten is contaminated or ground incorrectly. Grind longitudinally, not around, with a dedicated disc. The grind lines should run straight down the tip.
Per manufacturer specs, a tip angle of 15 to 20 degrees works best for most TIG tasks.
Contamination from touching the puddle: It happens to everyone. When your tungsten dips into the weld pool, it picks up metal. The result is a bright green or yellow tip on pure tungsten, and the arc starts spraying.
You'll also see inclusions in the weld bead. Stop welding, re-grind the tip, and restart.
Aggregate reviews from TIG manufacturers indicate that a clean, sharp tungsten is more important than almost any machine setting. That's because the arc shape and stability come directly from the electrode tip. If your tungsten looks rough, so will your weld.
If you're using an AC polarity for aluminum, the tungsten tip needs a ball formed at the end. But on DC, always grind to a point. Know the difference before you strike the arc.
Watch the Puddle, Not the Dial: Torch Angle and Speed Clues
The puddle tells the whole story. A clean, round, stable puddle means your setup is right. A puddle that boils, spatters, or crawls sideways shows a problem.
Torch angle matters more than most welders think. Keep a travel angle of 10 to 15 degrees, pushing forward along the joint. Keep the work angle near 90 degrees.
If you tilt too far, the gas stream slides off and oxidation follows.
Travel speed is just as critical. Go too slow and the bead washes out with grey edges. Go too fast and you get poor fusion at the toes.
Our research suggests a steady rhythm of about 2 to 3 dips per second is a good starting point.
Arc length is the last piece. A long arc spreads heat and pulls in air. A short arc risks touching the tungsten.
Keep the arc gap close, around the same diameter as your tungsten. If you're new to TIG welding basics, this consistent arc length is the first habit to build.
Filler Rod Technique: Dabbing, Dipping, and the "Stacked Dimes" Myth
People obsess over the stacked dimes look. That's a natural result of rhythm, not something you sculpt with your hand. The key is consistent heat and consistent filler feed.
Use the dabbing method. Dip the rod into the leading edge of the puddle, then pull it back. Keep the rod tip inside the gas shield the whole time.
If you pull the rod out of the shield, it oxidizes and you drag that contamination back into the next dip.
The common mistake is dipping too deep or too far forward. That creates cold spots and rough ripples. Instead, touch the rod to the puddle's front edge and let surface tension pull the metal in.
A 1/16-inch filler rod is forgiving for most sheet metal work.
If your bead has irregular spacing, slow down your hand. Count your dips in sync with your travel. You don't need fancy filler.
You need a steady hand and a clean rod. Your overall approach matters less than this consistent rhythm.
Aluminum vs Steel vs Stainless: Different Beads, Different Fixes
Each material fails differently. Steel gives you the widest margin for error. Stainless punishes heat.
Aluminum punishes contamination and technique.
On aluminum, the oxide layer is the enemy. If the bead looks grey or sooty, your AC balance is wrong or the surface isn't cleaned properly. Aluminum welds need a tight arc and fast travel.
A slow, wide puddle creates porosity as hydrogen escapes.
Stainless hates heat. A blue or purple weld means you've cooked the chromium away. That kills corrosion resistance.
Stainless also moves from heating and cooling, so a warped joint looks ugly even if the bead is clean.
Steel is more forgiving. If a steel bead looks bad, you usually have a contamination or gas problem, not a heat problem. When it comes to how the two arc processes stack up, TIG gives you unbeatable control but less tolerance for error.
For aluminum, follow aluminum-specific guidance from the start to save yourself the rework.
The Dirty Metal Trap: How Prep Ruins Perfect Settings
Here's a hard rule: prep is 50 percent of a good TIG weld. The settings only work on clean metal.
Oil, paint, grease, and even skin oil from your fingertips cause porosity and soot. Acetone is the standard solvent for stainless and aluminum. Wipe it on with a fresh rag, then let it dry completely.
After that, use a dedicated stainless wire brush to remove oxide layers.
Don't skip mill scale. On hot-rolled steel, mill scale has a higher melting point than steel itself. It traps the arc and creates a rough, dirty bead.
Grind it back to bright silver metal before you start.
Your gloves contaminate filler rods. If you touch the rod with a greasy glove, that oil goes straight into the puddle. Store rods in a sealed tube and keep a clean pair of gloves just for handling filler.
For steel-focused weld prep, this simple habit fixes most ugly bead surprises.
When the Front Looks Clean: Checking the Backside for "Sugar"
The front of the weld can look perfect. Flip the metal over, and there's dirty sugar on the back. That's oxidation from missing back purge.
This is a huge issue on stainless steel pipe and tube. The argon blanket protects the top surface only. The backside of the joint gets exposed to oxygen at red heat, and it grows a rough, crusty scale.
Welding pros call it sugar or oxide scaling.
The fix is back purging. Run a separate argon line from the back of the joint so the hot metal cools in an inert atmosphere. A flow rate of 5 to 10 CFH is usually enough, but bigger joints need more.
Per the American Welding Society, back purge is recommended for any sanitary or corrosion-critical stainless weld.
You'll also see sugar when there's a gap in the joint fit. If the parts don't sit tight, the purge escapes and air sneaks in. Check the gap before you weld.
A clean backside matters just as much as a clean top bead.
Quick Visual Reference Table for Ugly Welds
Use this chart as a rapid diagnostic. Match your weld's appearance to the most likely culprit.
| Visual Sign | Likely Cause | First Fix |
|---|---|---|
| Grey, powdery soot | Contamination or gas disruption | Clean base metal, check drafts, verify flow |
| Blue or purple tint | Excessive heat or short post-flow | Lower amperage, extend post-flow to 5–10 seconds |
| Small pits or holes | Moisture, dirt, or hydrogen porosity | Wipe with acetone, preheat mildly, grind clean |
| Rough irregular ripples | Unsteady torch or filler rhythm | Brace your hand, dip rhythmically |
| Black edge on aluminum | AC balance too high | Reduce cleaning action, shift balance negative |
| Yellow or green tungsten tip | Touched the puddle | Re-grind the electrode, reduce arc length |
If the bead looks like the first row, revisit the soot section above. If the tungsten itself is damaged, that's your starting point.
Is Your Gas Flow Actually Correct? Rechecking the "Correct Settings"
The dial on your regulator lies sometimes. A flow gauge can read fine while the torch delivers far less argon.
Check the whole path first. Look for kinks in the hose, loose fittings at the regulator and torch, and a worn or missing O-ring. Even a tiny leak at the torch head pulls air into the gas stream.
Gas flow numbers also shift with cup size. A #6 cup runs well at 15 to 18 CFH. A #8 cup or gas lens wants closer to 20 CFH.
After you set it, verify with a separate flowmeter if possible.
Pre-flow and post-flow are easy to ignore. Set pre-flow at 0.5 to 1 second so argon is in place before the arc starts. Set post-flow at 10 seconds for anything thicker than 1/16 inch.
This alone clears up a surprising amount of discoloration.
Bench Habits That Keep TIG Beads Clean Every Time
Good welds start before you pull the trigger. Build these habits into every setup.
- Keep a dedicated stainless wire brush. Use it only on one metal type, never on dirty steel.
- Store filler rods vertically in a sealed tube. Touching them with oily gloves is contamination.
- Wipe the base metal with acetone immediately before welding. Even "clean" metal has a film.
- Check your tungsten tip before every joint. A contaminated tip ruins the next weld before you start.
Routine inspection is cheap. Rework is expensive. A 10-second check of torch, tungsten, and gas line beats grinding out another bead.
FAQs: Ugly TIG Weld Troubleshooting in 60 Seconds
Why is my TIG weld black and sooty?
Black soot means contamination. The usual sources are oily base metal, a draft pulling the argon away, or a filler rod touched with greasy gloves. Clean everything, shield the work area from air movement, and keep rods sealed.
That combination cures most soot problems in under a minute.
Why does my weld have small holes or porosity?
Porosity comes from gas trapped as the puddle solidifies. Moisture is the main suspect, either from humid air, damp base metal, or a leaking gas line. Acetone cleans surface moisture.
A longer pre-flow and post-flow keeps the atmosphere stable. If it persists, check your argon bottle purity.
Why is my stainless steel weld turning blue?
Blue heat tint means the weld cooled in open air. Either your post-flow is too short, the gas flow is too low, or you're welding too hot. Reduce amperage by 10 percent and extend post-flow to 8 seconds.
That shift usually brings the color back to straw or silver.
Why is my TIG bead not stacking evenly?
Uneven ripples come from an inconsistent travel speed or filler feed. Steady your torch hand with your off hand on a brace. Dip the filler on a regular beat, like every second.
Practicing straight beads on scrap steel builds the muscle memory faster than any settings change.
Why does my aluminum weld look grey?
Grey aluminum means the oxide layer wasn't cleaned off, or the AC cleaning action is too aggressive. Brush the surface until it looks matte silver, then set your AC balance toward the negative side. A grey streak can also mean the torch was traveling too slow.
Speed up slightly.
