The same light asks for two different jobs
This is where most Breville owners go wrong, and it is the manufacturer's fault rather than theirs. On machines like the Barista Express, one indicator is labelled CLEAN / DESCALE and it means two entirely different things depending on how it behaves.
Flashing means the machine wants a cleaning cycle. That is a chemical backflush: a tablet dissolves in the group head and clears coffee oils out of the shower screen and the three-way valve. Solid on means it wants descaling, which is a different chemical doing a different job, dissolving mineral scale out of the boiler and the water path.
Run a descaler when the machine asked for a clean and you will not shift the coffee oils, because descaler is an acid for limescale, not a detergent for fats. Do it the other way round and the scale stays put. Descaling has its own step by step guide, linked at the foot of this page. Everything below is the cleaning half.
Newer machines are clearer about it. The Barista Pro says FLUSH on the LCD when it wants a cleaning cycle, and the Bambino Plus flashes the 1 CUP and 2 CUP buttons alternately, roughly every 200 extractions.
The cleaning cycle, step by step
You need the cleaning disc and a cleaning tablet, both of which came in the box, plus an empty drip tray and a full water tank. Breville's own sequence on the Barista Express runs like this.
Sit the cleaning disc in the 1 cup or 2 cup filter basket, put the basket in the portafilter, and drop one cleaning tablet into the filter on top of the disc. Lock the portafilter into the group head as you would for a shot. Turn the machine off. Then press and hold 1 CUP, 2 CUP and POWER together for 3 seconds.
The cycle runs about 5 minutes and beeps twice when it finishes. Take the portafilter out and check the tablet has completely dissolved. If any of it is left, turn the machine off and run the cycle again, because a partly dissolved tablet means the cycle did not do its job.
The trigger differs by model even though the procedure does not. On the Barista Pro you press MENU, turn the GRIND AMOUNT dial to FLUSH, select it, and press 1 CUP to start. On the Bambino Plus you hold 1 CUP and 2 CUP together for about 5 seconds, then press either button to begin, using the 1 cup dual wall basket and a 2 litre container underneath. Check your own manual for the exact combination, because Breville changes it between generations and between the US and other markets.
The steam wand, which is the part that actually goes wrong
Milk proteins bake onto a hot wand in seconds and set like glue. The habit that prevents every steam wand problem takes about ten seconds and belongs at the end of every milk drink, not at the end of the week.
Wipe the wand with a damp cloth as soon as you finish texturing. Then point it into the drip tray and briefly turn the steam on to blow out the milk sitting inside the tip. Wiping alone leaves the inside coated, and the inside is what blocks.
When a tip does block, set the steam dial to STANDBY, switch the machine off and let it cool. Breville's cleaning tool has a pin on one end for clearing the holes. If that does not free it, the same tool has a spanner in the middle: unscrew the tip, soak it in hot water, clear the holes with the pin, and screw it back on.
A wand that steams weakly or spits is almost always a partly blocked tip rather than a failing machine, and it is a five minute fix rather than a service call.
Portafilter, baskets and the group head
Knock the puck out, then rinse the basket and portafilter under the tap after each session. Coffee oils go rancid, and a basket that smells stale will make every shot taste stale no matter how good the beans are.
The fine holes in the basket block up gradually and quietly, which shows up as uneven flow and shots that run strangely. The fine pin on the cleaning tool clears them. Single wall baskets benefit from running water through the portafilter with no coffee in it, using the manual pour function.
For the group head itself, wipe the underside and the shower screen with a damp cloth to shift grounds. Periodically run water through the machine with the portafilter locked in and no coffee in the basket, which rinses the residue out of the path. On most models the shower screen can be removed and scrubbed when wiping stops being enough.
The grinder, if yours has one
Every Barista and Oracle machine has a grinder inside it, and grinders accumulate oil on the burrs that no amount of cleaning the coffee side will touch. Breville's routine is straightforward: unlock and remove the hopper with the beans in it, refit and lock it, then run the grinder until it empties itself. Unlock and remove the hopper again, take out the upper burr, and brush both burrs and the chute with the burr brush.
Do not wash burrs. They go back in dry, brushed only.
If the grinder is blocked between the burrs and the outlet rather than merely dirty, Breville documents a deeper strip involving a 10 mm socket, the grind fan and its washers. That is worth doing carefully and worth reading your own manual for first. Breville's warning is worth repeating: the burrs are extremely sharp.
What to do and how often
After every milk drink: wipe the steam wand and purge it into the drip tray. This is the one that matters most and takes the least time.
After every session: knock out the puck, rinse the basket and portafilter, wipe the group head.
When the machine asks, roughly every 200 shots: run the cleaning cycle with a tablet. Do not put it off, because the oils that build up in the three-way valve are what eventually make a machine leak or run slow.
Every couple of months: replace the water filter in the tank. Breville is explicit that this reduces how often you need to descale, so it is the cheapest maintenance on this list.
Occasionally, or when grinding gets inconsistent: brush the burrs and the chute.
None of this is a deep clean you set aside an afternoon for. It is five small habits, and machines that get them tend to outlive machines that get an annual rescue.