Even after 11 years of burning rod and pushing wire, welding will still find a way to keep you humble.

During one of our recent hands-on welding classes in Northern Colorado, a student and I ran into a classic shop nightmare: MIG weld porosity. The bead profile looked great, but suddenly, tiny pinholes started popping up across our test coupons.

If you’re learning how to weld—or trying to fix messy welds in your home garage—porosity is one of the most frustrating obstacles you’ll face. Here is how we systematically troubleshoot MIG weld pinholes, and the crazy lesson this specific class taught us.

Step-By-Step Checklist to Fix MIG Weld Porosity

99% of the time, weld porosity is caused by operator error or minor setup mistakes. Whenever students in our beginner welding workshops run into pinholes, we go down this exact troubleshooting checklist:

1. 📐 Check Your Technique: Keep your stickout distance consistent and maintain a steady travel speed. Moving too fast or holding the gun too far away starves the puddle of gas.
2. 💨 Verify Shielding Gas Flow: Ensure your gas bottle isn't empty, your flow meter is set correctly (typically 20–25 CFH for standard MIG), and there are no kinks in your gas hose.
3. 🧼 Prep Your Base Metal: Mill scale, rust, paint, oil, and moisture are prime culprits for porosity. Grind your steel clean down to bright metal before striking an arc.
4. 🌬️ Watch for Drafts: If you are welding near an open shop door or running a fan, the breeze can easily blow away your shielding gas envelope.

When It’s Not You: The Rare MIG Wire Issue

During this class, we checked every single box above. We fixed the technique, verified gas flow, ground the metal clean, and even turned off the shop fan.

Still, porosity everywhere.

There was only one variable left: the MIG wire spool.

Now, I’ve burned through thousands of pounds of wire in over a decade of metal fabrication, and while I’ve seen bad flux-core wire, I’ve never had a factory-defective spool of solid hard wire. But sure enough, we pulled off the half-used spool, dropped in a fresh roll of solid wire, and struck an arc.

Boom—instant, buttery-smooth, clean bead.

It turned out that specific section of wire had a bad alloy mix right from the factory.

The Big Takeaway for Beginner Welders

We always tell students in our Northern Colorado welding school: "Blame the rider, not the horse." Always troubleshoot what you can control first—your hands, your setup, and your prep work.

But when you’ve eliminated every variable and your welds still look rough, don't beat yourself up. Every once in a blue moon, it really is the equipment giving you grief!

Ready to Learn to Weld in Northern Colorado?

Troubleshooting issues like this is half the fun of learning the trade! If you've been wanting to learn metal fabrication, build your own projects, or just gain a badass new life skill, come hang out in our shop.

We host a 3-Hour Hands-On Welding Crash Course designed specifically for beginners across Fort Collins, Loveland, Greeley, and all of Northern Colorado.

• 🛠️ No experience required—we supply all the gear, tools, and metal.
• ⚡ 1-on-1 instruction to fast-track your skills without the frustration.
• 🎟️ Great as an experiential gift or a weekend project boost!

Tap the link to check our schedule & grab a spot!

https://calendly.com/ironstudiollc/into-to-welding-class