Hi guys, Ryan here! As a coffee enthusiast, I’ve spent countless hours in coffee shops, observing the art of coffee making. Baristas work tirelessly to craft the perfect cup, but there are a few common mistakes I notice in coffee shops all the time. They might seem insignificant on the face of it, but they can impact the quality of the coffee a lot. In this post, I’ll share the three most prevalent mistakes I see — and I’ll also include the practical solutions we use and recommend at Iron & Fire so you can avoid them too.
If you only take three things away from this post, make it these:
- Don’t tap the portafilter after tamping — it can disturb the puck and increase the risk of uneven extraction (“channeling”).
- Clean your steam wand every time — a quick purge + wipe routine helps prevent clogs, watery milk, and hygiene issues.
- Never reheat / re-steam milk — it ruins texture and can increase food-safety risk if milk has been sitting around.
Quick barista basics (definitions)
We’ll keep this simple:
- Puck: the compressed bed of ground coffee in your portafilter basket.
- Channeling: when water finds an “easy path” through weak spots in the puck, causing uneven extraction.
- Microfoam: fine, silky milk texture created by steaming (the goal for latte-style drinks).
- Purge: briefly opening the steam valve to clear water/condensation or residue from the wand.
Mistake #1: Tapping the portafilter after tamping
What I mean by this
After tamping, some people tap or knock the portafilter to tidy the rim or “level things out”.
Why it matters (in plain English)
Once your puck is tamped, tapping can create cracks or weak spots in the coffee bed. That raises the chance of channelling, which means water rushes through parts of the puck instead of extracting evenly. The result is espresso that tastes inconsistent — sometimes sharp/sour and bitter at the same time.
It can also dent or damage your tamping station or equipment over time. It’s one of those habits we see a lot, and it’s an easy one to fix.
What we recommend (simple workflow)
- Dose coffee into the basket
- Distribute evenly (so the bed is level)
- Tamp once, level
- Don’t tap after tamping — lock in and brew
What to do instead of tapping
- If you need a neat rim: wipe the basket rim rather than knocking the handle.
- If you’re trying to level grounds: do it before tamping (distribution tool / WDT), or use a gentle palm tap before tamping (not after).
If / then troubleshooting (espresso)
- If your shot runs fast and tastes sharp/sour: go a touch finer and make distribution more even before tamping.
- If the flow is uneven or spurting: stop post-tamp tapping; focus on even distribution + a level tamp.
- If the shot chokes or barely drips: go slightly coarser or reduce dose; keep puck prep consistent.
Quick reference: symptoms → likely cause → fast fix
| Symptom | Likely cause | Fix in 30 seconds |
| Shot runs fast + tastes sour | Under-extraction / channelling risk | Finer grind or better distribution + level tamp |
| Uneven flow/spurting | Channeling | Avoid post-tamp tapping; distribute evenly; check tamp level |
| Very slow shot/choking | Grind too fine / overdosed | Coarsen slightly; reduce dose; keep prep consistent |
Mistake #2: Neglecting steam wand maintenance
What I see happening
This one is incredibly common: steaming milk, putting the jug down… and the steam wand doesn’t get cleaned properly (or at all). From our side, we see this show up as inconsistent milk texture and more “mystery problems” behind the bar than people realise.
Why it matters
A dirty or partially blocked steam wand can lead to:
- Worse steam performance (inconsistent steam power)
- Milk that turns watery, bubbly, or flat
- Build-up that becomes harder to remove (and less hygienic)
Our “10-second steam wand habit” (every drink)
- Purge before steaming (1–2 seconds) to clear condensation
- Steam milk
- Wipe immediately with a clean damp cloth
- Purge after steaming (1–2 seconds) to clear residue
Simple maintenance checklist
- Every drink: purge + wipe + purge
- End of day: clean the steam tip properly (follow your machine guidance) and wipe the wand thoroughly
- If you notice weak steam or odd milk texture: check for partial blockage and deep-clean
Mistake #3: Reheating milk (or re-steaming milk)
What I mean by this
Reheating milk that’s already been steamed — either by steaming it again, or trying to warm it back up after it’s been sitting.
Why it matters
- Texture suffers: microfoam breaks down, so milk becomes flatter and less enjoyable.
- Food safety risk: milk that’s been sitting and cooling can become higher risk if handled poorly — which is why coffee shops typically avoid it as a rule.
What we recommend (and what I do)
- Steam fresh cold milk each time
- Reduce waste by using the right jug size for the drink (smaller jug for one drink; larger for multiple)
Milk temperature guide
A good target for milk-based coffees is around 60–70°C. Going much hotter can make milk taste less sweet and makes good texture harder to achieve.
Printable checklists + quick assets (save or share)
Checklist: Espresso puck prep (to reduce channeling)
- Dose consistently
- Distribute evenly (no obvious clumps)
- Level the bed before tamping
- Tamp once, level
- Don’t tap after tamping
- Lock in and brew promptly
Checklist: Steam wand hygiene (every drink)
- Purge before steaming
- Steam
- Wipe immediately
- Purge after steaming
- Keep a dedicated clean damp cloth for the wand
“Busy service” quick wins
- If espresso tastes inconsistent: fix puck prep first (distribution + no post-tamp tapping)
- If milk texture is bubbly/watery: fix steam wand routine first (purge + wipe)
- If you’re tempted to reheat milk: switch to smaller batches / smaller jugs
Related reading
FAQs
Why is tapping the portafilter after tamping bad?
Tapping after tamping can crack or disturb the puck, creating weak points where water rushes through. That increases the risk of channeling and uneven extraction, which can taste inconsistent (sometimes sour and bitter at the same time). We recommend distributing and levelling before tamping, tamping once, then locking in and brewing.
What is espresso channeling and how do you spot it?
Channeling is when water finds an easy path through the puck instead of extracting evenly. You may notice uneven flow, sudden spurts, fast blonding, or inconsistent flavour. The quickest fixes are improving distribution, tamping level, and keeping grind/dose consistent.
Should you purge the steam wand before steaming milk?
Yes. A brief purge clears condensation so you don’t inject water into the milk. Purging after steaming helps clear residue from the tip. Combine this with an immediate wipe using a clean damp cloth for more consistent microfoam and better hygiene.
How often should you clean a steam wand?
At minimum: every drink. Purge and wipe immediately after steaming, and ideally purge before steaming too. Then do a regular deeper clean (end-of-day routine and periodic tip cleaning) so residue doesn’t build up and affect steam performance and hygiene.
Can you re-steam milk (or reheat leftover milk)?
It’s best avoided. Re-steaming milk usually gives worse texture because microfoam breaks down, and it can increase food-safety risk if the milk has been cooling and sitting. We recommend steaming fresh cold milk each time and reducing waste by using the right jug size.
What temperature should you steam milk to?
A common target for milk-based coffees is around 60–70°C. It’s hot enough for sweetness and texture without pushing into “too hot” territory where flavour and texture can degrade. A thermometer is useful until you learn the feel.
Why is my milk bubbly instead of silky microfoam?
Bubbly milk often comes from technique issues or inconsistent steam. Common causes include not purging the wand (adding water), poor wand cleanliness (partially blocked holes), or overheating. Try purge → steam → wipe → purge, and focus on creating a smooth “rolling” motion in the jug once you’ve introduced a small amount of air.
If you’re working on your home coffee setup or just want better café-quality drinks, we’ll be sharing more simple barista tips like this. Have a browse of our other guides — and if you fancy trying something new, explore our freshly roasted coffees.
