Hairline cracks in the mortar. How do I fix a hair line crack?

I have a crack in the front mortar. I properly did the 6 days of slow firing. This is my second full fire to make pizzas. Can I fix this?

Super Easy (and inexpensive) Fix!

When the oven is warm, simply squeeze some High-Temperature Mortar into the crack.

In about 3 minutes it will be hard… then in 2 hours, it will be rock-hard and resistant to future cracking.

EXTERIOR (Tan / Buff Color)

INTERIOR (Black / Soot Color)

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I finished my third curing fire and noticed this hairline crack. Its to small to apply mortar and not deep. Any advice?

This one I wouldn’t worry about, at least for now.

It doesn’t appear to reach the edge of another joint. Compare your photo with the one up thread, and you’ll see that’s a crack that goes through more than one course, and from the chimney.

If it gets deeper/longer/wider, then @BrickWood’s advice would apply.