Affordable, full featured, automatic machine that can make a really good cup, but may have sacrificed long-term durability for a lower price.
Positive Product Points
Easy to use. Great for the beginner to moderately advanced enthusiast. Good features for the price, even at the full price of a new machine. Excellent steaming capability. Decent espresso out of the box, and pretty darned good once paired with a good grinder and non-pressurized filter baskets. Large water reservoir.
Negative Product Points
Frame flexes when tightening portafilter. Non-standard portafilter size (53mm). Annoying filter basket retaining lever. Drip tray is too small. No lip on rear of cup tray. Cups can fall off the back when removing water reservoir for filling. Built-in tamper is useless.
Overall Materials: I purchased this machine used from a private seller. When I received it, the unit had already seen some amount of moderate use. The first thing I did was disassemble the casing to check all the internal connections and to ensure that no packing material had migrated inside the machine. What I found was a combination of encouraging and slightly disappointing. The good things were that all wiring was secured with cable ties, the circuit boards were securely held in place, and that a good deal of the interior space is taken up by a fairly heavy marine-brass boiler. The bad: plastic water lines from the pump to the boiler held on with clamps, and cup tray heater elements that are easily dislodged.
The plastic lines may or may not be a future leak problem. I'd prefer to see brass lines everywhere with compression fittings, but I also understand that this is a sub-$500 machine. The cup tray heating elements are ceramic with soldered bare wire leads and are held to the aluminum tray with spring clips. These clips may become dislodged if the unit is moved roughly, leaving both a loose piece of spring-steel rattling around in the internals as well as uninsulated leads possibly coming into contact with other metal, causing a short. I secured these elements in their slots with high-temp epoxy to prevent this from happening.
Overall construction is generally good, with everything fitting flush, no sharp edges, and few seams for drips, spray, or grounds to permeate. The frame could be more solid, and it tends to flex with the effort of tightening the portafilter to the grouphead. The base and front body panels are plastic, which may worry some, though it would take a good drop to break them and they're easy enough to keep clean. The flexion of the frame has not caused any gaps or cracks in the plastic parts. The built-in tamper is molded into a plastic panel, isn't the right size for the baskets (it's slightly smaller), and requires that you hold the machine in place while applying upward pressure.
The portafilter is a dual-spout home-machine type of 53mm diameter. It's of fairly heavy chromed brass, however, and does retain heat well. The molded plastic handle is adequate and fits the average hand fairly comfortably. The filter baskets are held in place only by a manually-operated plastic latch which could be prone to breakage if abused.
Operation: The water reservoir holds three liters and can be filled in place or removed to the sink. There is no pump inlet tube in the tank - it drains from the bottom. A spring valve lets you remove the water tank while still partially full. The tank is clear and is slightly wider than the machine body - you should be able to see the water level from either the front or sides of the unit.
Initial warm-up is fairly fast - about 2-3 minutes from power-on until the boiler comes to operating temperature. It takes about another 15 minutes for the grouphead and portafilter temperatures to stabilize, but you can force-heat the machine by running water from the steam wand and grouphead. Force-heating readies the machine for your first shot in about 6-7 minutes from power-up.
The machine is a fully-automatic type, automatically dispensing any of 12 preset volumes (six single, six double) of water through the head. However, most folks will only use settings "1" (ristretto) and "2" (espresso), or "0" (manual dosing). The higher volumes simply over-extract the grounds, producing a bitter beverage. If one desires an Americano, it's best to pull a double espresso shot at "2" and then top off the cup with water from the steam wand rather than setting the brew dose to "6". When using the pre-programmed volumes, one has the option to select a single or double shot, which works dependably.
Initially, the machine comes with two pressurized "crema-enhancing" filter baskets, a single and a double, as well as a pod-adapter. The pressurized baskets produce an adequate espresso even with a sub-par grind and the light tamp to which the built-in tamper limits you. However, the machine will produce a very good espresso, indeed, if one uses a proper grind, a properly-sized metal hand-tamper, and the non-pressurized baskets that are available from the importer (Baratza).
The SL-90 has a single boiler, so one must switch between brewing and steaming. It takes about 45 seconds for the boiler to come up to steam temperature. Once it does, it produces large volumes of steam through the wand. The steam wand swivels directly out from the body of the unit, and has a single-hole tip without "E-Z Froth" gadgets. With practice, the Solis will provide you enough steam to beautifully micro-froth milk. The pump does not run while steaming, so you must replenish the boiler when going back to brewing by leaving the steam valve open until the boiler is depressurized, and water runs from the wand. The boiler ready light will indicate when you can shut off the wand valve.
Controls: All brew controls are touch-sensitive and placed behind a durable, wipeable membrane panel. Unless you have ham-hands and abuse the buttons, they should last for quite a while. The main power, steaming, and cup warmer switches have indicators to show when they are on. The single and double brew buttons light when brewing is in process. A single, bright green, numerical LED display shows the brew volume (0-6). The boiler and steam temperature indicators are bright LED's that switch from red to green to indicate readiness.
The steam/hot water valve is on the right side of the machine and turns toward you to open and away to close. On opening, a microswitch activates the boiler heating element to maintain steam pressure or hot water temperature during steaming or dispensing.
Overall: Construction - Solid boiler, good wiring and harnesses, and fit is adequate. Would be nice if frame was stiffer. I'd like to see the plastic body panels replaced with sheet metal.
Aesthetics - not a looker, really. The black model is probably more "spiffy" looking than the white. Not an ugly machine, really, but those looking for brushed stainless and chrome will be disappointed.
Operation - Easy enough to set up, fill, and use.
Controls - Buttons are small-ish, but usable. No more complex than they need to be.
Brewing - Pressurized baskets allow beginners to produce a drinkable espresso from the start. Good pump pressure and availability of standard filter baskets allow the more advanced enthusiast to brew a very good drink with the proper grind and tamp.
Steaming - Excellent steam capacity. The simple wand produces wonderful froth once you learn how to use it.
Hot water - Will dispense 8 oz. of water with a final temperature of around 185F. Great for green and oolong teas, but perhaps a bit cool for optimal extraction of black leaf varieties.
Value - Hard to beat for the price. At this cost level, it's a choice between the automatic features of the SL-90 and (at around $30-40 more) the heavier construction of the Rancilio Silvia.
The result is much better temperatures at the cup and the end of underextraction. Shots that were slightly sour are now perfectly balanced. The sole drawback is that until the machine stabilizes, the higher thermo setting results in false pressure in the boiler. You can either let the machine idle for 15 minutes after power-on, or bleed the false pressure from the steam wand.
Nothing has broken in the course of the last three months. I performed a descaling and cleaned residue from the steam wand tip. Performance has been remarkably stable, and my coffee has steadily improved.
One thing I have noticed when experimenting with drinks such as the espresso lungo and cafe crema - the water flowrate is fairly low on this machine. Trying to produce larger volumes results in water being in contact with the grounds for way too long, leading to over-extraction. That being said, the Solis SL90 is producing excellent espresso, Americanos, and milk drinks.
At the three month mark, I'd buy it again for the price - with reservations. I'd want to try a few other semi-auto machines in its price range for comparison's sake.
One Year Followup
More than a year later, the SL-90 is still cranking out the goods. Maintenance has been restricted to general cleanliness, with a thorough scouring of the grouphead every 3-4 weeks. The portafilter handle/body goes into the dishwasher once a week or so to get clean. At six-month intervals, I've been descaling.
Am I still happy with the unit? It's still performing consistently. And with finicky home appliances that involve boilers, pumps, and electronic control systems, that's pretty significant praise. Have I outgrown it? Not really. I've got machine envy, of course - who wouldn't love a plumbed-in heat-exchanger unit on their counter?
The only thing I would improve would be the flow rate. It's just too low for lungos and cafe cremas. The water's in contact with the grounds for too long brewing those beverages, and it shows in a sharp bitterness. This could, of course, just be my machine - which is several years old at this point - but it seems to be a common complaint about the SL70/90 units.
So, at this point, I can say that this machine is still adequately serving my requirements. With unpressurized baskets, it's making great espresso. My other drinks (Americanos and the occassional cappucino) that use that espresso as a starting point are likewise very good. It still steams like a champ, too.
If I were shopping for a first machine, while knowing what I know now, the SL90 would still be a viable choice. If the SL90 blew up today, I'd probably use it as an excuse to upgrade, but I'd buy another at the right price if that was the extent of my budget.