Few things sting worse than pulling the torch away from a beautiful bead only to watch a tiny hole appear where the arc died. That’s the TIG weld hole when stopping arc, and it’s one of the most common defects in gas tungsten arc welding. It happens because the molten puddle shrinks as it solidifies, leaving a crater at the end of the weld.
That little cavity can crack, leak, or ruin a clean pass.
In our research across manufacturer manuals and welding standards, the fix comes down to one skill: shutting the arc down the right way. Most inverter machines let you set a downslope of 2 to 5 seconds and a post-flow time of about 1 second per 10 amps. Use those features, and you eliminate most crater holes before you even change your technique.
Let’s break down why this happens and exactly how to stop it.
Quick Answer
A TIG weld hole when stopping arc is a crater left by the shrinking puddle. It forms when you cut the amperage too fast or skip the final filler dab. Fix it by easing off the pedal and adding one last dab.
Then hold the torch in place until post-flow ends.
Why a Hole Appears When You Stop the Arc
Think of a TIG weld as a moving puddle of molten metal. The process itself uses an arc to melt the base metal, and you steer that puddle along the joint. When you shut the arc off, the heat source vanishes, but the puddle doesn’t freeze instantly.
It cools from the outside in, and the center is the last spot to solidify.
Here’s the problem. As that center cools, it shrinks. But the edges have already hardened into a stiff ring, so the shrinking metal has nowhere to go.
It pulls downward, forming a cavity called a crater. That’s the hole you see when you stop the arc.
If you cut the current instantly, the collapse is even worse. A sudden power drop doesn’t give the puddle time to settle or refill. It just leaves a hollow.
The Real Culprit: It’s Not Always Your Amperage
High amperage can certainly deepen the crater. A huge, fluid puddle has more volume to shrink, and if your travel speed leaves you behind your own heat, the stop gets messy. But most of the time, the current isn’t the real problem.
The real culprit is how the arc dies. An abrupt shut-off slams the puddle from full heat to zero, and the liquid metal collapses. That’s why a machine with downslope helps.
It slowly lowers the amperage and gives the puddle time to close in on itself.
What That “Mouse Hole” Actually Means
In the workshop, you’ll hear people call this a mouse hole. The crater often looks a little cracked and hollow, like something gnawed on the end of the bead. On a structural weld, it’s a stress riser.
On a gas or fluid line, it’s a leak waiting to happen.
Per AWS D1.1 structural welding code, a visible crater that contains cracking is often grounds for rejection. So this isn’t just cosmetic.
The Quick Fix: Fill the Crater
The quick fix is simple: add filler metal right before you stop the arc. That final dab fills the void as the puddle solidifies, so there’s no hole left behind. One dab is usually enough, and if you time it right, the weld end looks just as full as the rest of the bead.
The One Motion That Saves Every Weld End
Here’s the motion. With the puddle still hot and smooth, dip the filler rod into the front of the puddle and pull it out. Almost immediately, ease off the foot pedal.
You’re not trying to add a big pile of filler. You’re replacing the metal that would otherwise shrink away.
Think of it as feeding the crater before it exists. If you’ve watched a pro finish a weld, it’s not a dramatic move. It’s a small, controlled drop of filler, then a gentle power-down.
When a Single Filler Dab Is Enough
On most material up to about 1/8 inch thick, one dab of matching filler rod is plenty. If the puddle is wider than your filler rod, you might need two dabs. Start with one and get comfortable with the timing.
If the crater looks concave after you cool, you didn’t add enough. If you’ve piled up a lump, you added too much. The ideal end looks flat and filled, with no dip at the center.
Getting that puddle size right is part of mastering different welding techniques, but this habit applies to every TIG job.
Crater Holes 101: What’s Happening Inside the Puddle
To fix a crater hole, it helps to understand what it actually is. There are two distinct causes: shrinkage and gas porosity. They look similar from the outside, but they form differently.
Shrinkage Cavity vs Gas Porosity
A shrinkage cavity is a physical collapse. The puddle loses heat, solidifies from the edges, and the center pulls down as it shrinks. That’s the classic TIG crater hole.
Gas porosity is smaller. Tiny bubbles of shielding gas get trapped in the puddle as it freezes, and when they break through the surface, they leave pinholes. You often see these clustered together near the weld end.
They happen when the gas shuts off too early or when the base metal is dirty.
Why Aluminum and Stainless Behave Differently
Aluminum has a high shrinkage rate. When it solidifies, it pulls hard, so an unfilled crater on aluminum is deep and prone to cracking. That’s why aluminum joints, especially on boats or trailers, often fail right at the stop point.
Stainless has a different quirk. Its thermal expansion is higher than plain carbon steel, so the area around a crater is under more stress. As the puddle contracts, the weak center can tear open into a crater crack.
| Material | What You’ll See at the Stop | Best Habit |
|---|---|---|
| Mild steel | Shallow crater, usually easy to fill | One dab plus pedal ramp-down |
| Stainless | Crater cracks near thin edges, pinholes | Slow downslope plus post-flow |
| Aluminum | Deep crater, cracking on the final pass | More filler on the last dab |
Choosing the right approach for aluminum means planning for that extra shrinkage. The same rule applies to steel, but the stakes are lower.
Essential Setup: Machine Settings That Save Your Weld End
Great stop technique starts before you strike the arc. If your welder has downslope and post-flow, use them. As of 2026, both features are standard on most mid-range TIG units, and even budget inverter machines usually offer them.
Downslope / Current Ramp-Down: What It Does and How to Set It
Downslope controls how fast the current drops after you release the pedal. It does the braking work for you. Without it, the arc dies instantly.
With it, the puddle stays fluid for a few extra seconds and has time to close in.
A good starting point is 2 to 5 seconds. On thin stainless, keep it around 2 to 3 seconds. On aluminum, lean closer to 5.
If your machine doesn’t have downslope, mimic it by easing the pedal off over about 3 seconds.
Post-Flow: The Hidden Gas Shield You’re Probably Skipping
Post-flow is the shielding gas that keeps flowing after the arc goes out. It protects the hot tungsten and the cooling puddle from oxygen. If you lift the torch as soon as the arc dies, the crater is still orange-hot and exposed to air.
That’s how pinholes form.
The general rule is one second of post-flow for every 10 amps of final current. At 150 amps, hold for about 15 seconds. It feels long the first few times.
It’s worth it.
Set argon flow to 15 to 20 CFH. Too little gas leaves the crater unprotected, and drafts can blow the shield away before the metal has cooled.
Foot Pedal vs Fingertip Throttle: Which Gives Better Stop Control
The foot pedal is the best setup for avoiding crater holes. You can ramp down smoothly with your toe, and your hand never touches the current. That keeps your travel steady while your foot handles the power.
A fingertip throttle on the torch can work, but it’s harder to be smooth. You’re moving your hand at the exact same moment you’re trying to hold the torch still. The result is often a wobble right at the stop.
If you’re fighting crater holes, a pedal gives you more control.
How to Stop a TIG Weld Without a Crater Hole (Step-by-Step)
This is the exact sequence we recommend after watching welders, both new and experienced, finish beads.
Step 1: Set Up Your Finish Before You Strike the Arc
Decide where the bead will end. Position yourself so you can finish in a comfortable spot, not with your arm stretched out. Set your downslope and post-flow before you start.
Clean the base metal and choose the right filler for steel or aluminum.
Step 2: The Final Filler Dab
When you’re about one rod-width from the end, dip the filler into the front of the puddle. Pull the rod out before the puddle swallows it. This adds a little extra volume that will feed the crater as the metal shrinks.
Step 3: Ease Off, Don’t Snap Off
This is where most crater holes happen. Don’t yank your foot off the pedal. Ease off over two to three seconds.
As the current drops, the puddle gets smaller and pulls together. Keep the torch still and let the filler settle into the center.
Step 4: Hold the Torch, Breathe, Then Lift
The arc is out, but the puddle is still cooling. Leave the torch in place while the post-flow gas blankets the weld. Count out the seconds you set earlier.
If you’re at 150 amps, that’s roughly 15 seconds. When the metal stops glowing, lift the torch.
The result is a filled, rounded end with no dip at the center. It takes practice, but once this sequence becomes muscle memory, you’ll stop seeing those little holes for good.
The Decision Tree: What's Causing Your Crater Hole?
If you're still seeing holes after following the stop sequence, you need to diagnose the exact failure. Use this quick decision framework to sort it out.
Is the Crater Deep and Concave?
A deep, hollow crater means the puddle collapsed before it could solidify. You probably cut the amperage too fast or skipped the final filler dab. If your machine has downslope, extend it to 3 to 5 seconds.
If it doesn't, ease the pedal off more slowly and add slightly more filler on that last dip.
Is the Crater Cracked?
A crack running through the crater means the shrinking metal tore itself apart under stress. This is common on stainless and aluminum. The fix is to keep the final dab generous and let the puddle solidify slowly.
Cracks also show up when you're welding edges that are too hot, so drop your amperage by 10 to 15 percent on thin sections.
Is the Weld End Full of Pinholes?
Tiny pinholes scattered across the stop point usually point to gas contamination. The shielding gas shut off too early, or the base metal wasn't clean before you started. Check your post-flow timer and give it more time.
Then be honest about your prep. Oils, paint, and even fingerprint grease produce porosity when they burn off.
Do You See Black Soot or Discoloration?
Black soot near the crater means the tungsten dipped into the puddle or the shielding gas flow is too low. You're burning material instead of melting it cleanly. Regrind your tungsten to a fine point and check your gas flow with a gauge.
For TIG welding, 15 to 20 CFH of argon is the standard range.
When You Can't Rely on Downslope
Not every welder has downslope. Entry-level machines and a lot of rigs older than 15 years just kill the arc when you release the trigger. You can still get a clean stop.
You just have to be more deliberate about it.
Working With a Basic Machine (No Downslope)
Without downslope, the amperage drops from full heat to zero in the blink of an eye. The puddle wants to collapse, so your filler dab has to do more work. Add a slightly larger final dab and let it wet out before lifting the torch.
Then hold the torch steady for the full post-flow cycle.
The Manual Ramp-Down Technique That Works
If you have a foot pedal, you already have manual ramp-down. You just need to train your foot to ease off over three seconds instead of lifting it. If you have a fingertip throttle, turn it down gradually while keeping the torch still.
The key is making the current fall in a slope, not a cliff.
Using a Filler Rod to "Kill the Puddle" Manually
One trick that works on machines without downslope is using the filler rod to absorb heat. After you shut the arc off, dip the filler rod into the puddle and let it sit for a half second. The rod pulls heat away and gives the shrinking metal something to grab.
It's an old trick, but it genuinely works.
Mistakes That Cause Crater Holes (And How to Break the Habits)
Most crater holes come down to four habits. Fixing them is just a matter of slowing down and paying attention.
Lifting the Torch Too Early
The arc is out, but the metal is still glowing. If you lift the torch early, the post-flow gas lifts with it, and the puddle oxidizes. Hold the torch in place until the glow fades.
Count it out if you have to. That extra 10 seconds costs nothing and saves the weld.
Snapping the Pedal Off Like a Light Switch
An instant shutdown gives the puddle no time to settle. The hotter the puddle, the harder it collapses. Make a conscious effort to ease off smoothly.
Think of it like easing your foot off the gas pedal, not stomping the brake.
Skipping the Final Filler Dab on a Shallow Puddle
Thin material makes you nervous, so you keep the puddle shallow. Then you stop, and the shallow puddle shrinks into a tiny hole. The solution is to trust the puddle and feed one light dab before the stop.
It will be fine. The dab is what keeps the end filled.
Running Too Hot for the Material Thickness
If you're chasing a wide, fluid puddle across thin steel, that same heat makes the crater worse at the stop. Drop the amperage until the puddle is about the width of your filler rod. Your final dab will do its job, and you'll see cleaner stops right away.
Quick Reference: Settings and Setup for Clean Weld Ends
Here's a table of starting settings that produce solid weld ends across common materials. Fine-tune from there based on your machine, your filler, and your joint fit-up.
| Material | Amperage Range | Downslope | Post-Flow | Notes |
|---|---|---|---|---|
| Mild steel | 90-130A | 2-3 sec | 8-12 sec | One filler dab, then ease off |
| Stainless | 70-110A | 3-4 sec | 10-15 sec | Watch for crater cracks |
| Aluminum | 130-180A | 4-5 sec | 12-18 sec | Generous final dab, slow ramp |
Downslope, Post-Flow, and Gas Flow by Material
Gas flow sits at 15 to 20 CFH for all three materials with a standard gas lens setup. If you're welding outside, bump it to 25 CFH to fight drafts. Post-flow follows the 1-second-per-10-amps rule, which is why heavier aluminum jobs need longer holding times.
Tungsten Prep for Clean Arc Starts and Stops
A contaminated tungsten is a silent killer of clean stops. If the tip touches the puddle, it picks up metal and spits at the notch. The arc becomes unstable right when you need it steady.
Grind the tungsten to a sharp point on a dedicated grinding disc, and switch to a balled tip for AC aluminum.
Real Scenarios: Where Clean Stops Matter Most
A crater hole isn't always a failure. But in certain industries, it absolutely is. Here's where it matters most.
Thin Stainless Tubes for Sanitary or Exhaust Work
Sanitary tube welds need a consistent internal bead with no pits. A crater hole on the inside of a tube is the perfect place for bacteria to hide. For exhaust systems, the hole is a stress riser that cracks under vibration.
A clean stop is the difference between a weld that passes inspection and one that gets cut out.
Aluminum Marine Repairs and Crack Sensitivity
Aluminum boats bounce and flex. A crater hole at the end of a seam crack will spread across the entire weld under that kind of load. Marine welders add a generous final dab and use a slower downslope specifically to avoid this failure.
It's part of doing aluminum welds right.
Fixed-Position Pipe Welding (Why Restarts Are Brutal)
When you're welding a pipe in the 5G or 6G position, you can't just start and stop wherever you want. Every restart has to blend into the previous stop. An unfilled crater leaves a valley that you have to grind out or feed filler into on the restart.
You can think of it as the hidden cost of not shutting down cleanly the first time.
Safety Notes: Post-Flow, Fumes, and Clean Metal
Why Ventilation Still Matters Even With Argon
Argon itself isn't toxic, but TIG welding still produces metal fumes and ozone. Weld in a ventilated area or use fume extraction per OSHA 29 CFR 1910 Subpart Q. A crater hole is a defect, but breathing fumes is a bigger risk.
Check Your Gas Lines Before You Blame Your Technique
A kinked hose or low cylinder pressure causes poor shielding and pinholes. Verify you have gas flow before you adjust your stop technique. A cheap flowmeter saves you a lot of head-scratching.
Frequently Asked Questions
Why Do I Get a Hole Even When I Add a Final Dab?
You either added it too early and it washed away, or you didn't hold post-flow long enough. Wait until the puddle wets out, then ease the pedal off slowly.
Does Pulse Mode Help With Crater Holes?
Yes, pulse mode lets the puddle cool slightly between pulses, which reduces the liquid volume that has to shrink. It won't replace a proper stop sequence, but it makes the crater shallower.
Can I Grind Out a Crater Hole and Weld Over It?
Yes, grind the crater to sound metal, and restart ahead of the ground area. Apply fresh filler as you blend back into the existing bead.
How Long Should I Hold Post-Flow?
Use one second per 10 amps of final current. At 150 amps, hold for about 15 seconds before lifting the torch.
The Bottom Line: Build a Clean Stop Into Every Weld
A Simple Pre-Weld Checklist for Better Endings
Set downslope, post-flow, and gas flow before you strike the arc. Every time, end with a final filler dab and a smooth pedal release.
When a Crater Hole Means a Failed Weld (and When It's Cosmetic)
A small crater on a non-critical shop project is cosmetic. A cracked crater on a pipe, structural joint, or tank is a failure. When in doubt, grind it out and re-weld.
