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For the last year, I have been working closely with Pullman Tampers to create a tamper for use with the EK43. This initially simple project has since evolved into a completely new tamper design – for use with any grinder – that markedly improves extraction, consistency, ergonomics, cleanliness and taste.

Diameter

A tamper’s diameter is very important, but it’s only one part of the story. Along with diameter, one should be measuring the effective tamping area. That is, the size of the area that’s actually compressing the coffee grounds. At first this seems quite simple, but almost all tamper manufacturers include a curved edge or ‘fillet’ on the bottom of their tampers. This feature reduces their effective tamping area by a startling amount. These diagrams will help you to understand how a tiny curve can have a big impact on your tamper’s effectiveness. Keep in mind that all of them are to scale, and assume that all VST baskets have an internal diameter of 58.7mm.

Tampers are perfect circles, and circles have a tendency to gain a lot of area as they get wider. A simple 1mm radius curve on a tamper can seriously reduce the flat area that is actually doing the work. The difference in area between a regular 58mm tamper with a 1mm curve and the Pergtamp is 2.25cm2 – a number that left me checking and double-checking my maths. How can a tamper possibly have 2.4 more cm’s of tamping area?! It’s all in the edge.

This tamper is designed for, and only suitable for use with, VST baskets. Their inner diameter is very consistent, which means a tamper with an outside diameter of 58.50mm will fit into every basket. VST baskets have a typical inner diameter of 58.50mm +/-0.15mm. No mean feat for a stamped part. The diameter of the Pergtamp is very deliberately 58.50mm +0.00 -0.05mm. This is to ensure that even with hot/cold shrinkage/expansion and circularity variances of the components, they will always work together. It also allows for a small amount of basket deformation or tamper damage without ill effect. If it doesn’t fit, or if you’re experiencing frequent channelling from the vacuum effect, the basket or tamper has been seriously deformed and should be replaced

Ergonomics & Cleanliness

Almost every barista has struggled with a coffee tamper jamming (special mention to Kyle Glanville, famed USBC competitor). In a busy shop it can be debilitating for speed and morale. With proper care, Pergtamp will never jam. It will also help keep your portafilter and tamping area cleaner by pushing every single coffee grind down rather than out of the basket.

Pergtamp will eventually be available as a base in both the ‘Barista’ and ‘Nexus’ style from Pullman tampers. I know a lot of Baristas that have strong opinions about these two styles, but for now it will only be available in the Nexus style. Buy it with a new handle or use your own – just make sure that you match the style of handle and base; they have different screw threads.

Extraction

A great test for any coffee brewing equipment is to measure whether it increases extraction yield. This isn’t necessarily to achieve a higher yield, but to determine if it is extracting the coffee more evenly. A more even extraction will have the water missing fewer coffee grounds, and hence increase extraction.

During my tests, the Pergtamp increased the espresso extraction yield from a 58.35mm tamper by an average of 1%. These results were obtained with both standard Mazzer Roburs and Mahlkonig EK43 grinders at the same grind setting with the same brewing parameters.

[25/6/14 Edit: This test may not be 100% replicable on your equipment. I used a La Marzocco Linea with 20g VST’s, a Mazzer Robur with 400kg of beans through the burrs, my own distribution technique and a certain style of espresso roast. Every espresso machine, grinder, shower screen, Barista, coffee etc. is a little bit different and may not result in exactly 1% more extraction (it might get you even more!). That said, I’m 100% confident every combination of equipment will result in a significant and noticeable increase in extraction yield and extraction evenness. I will be publishing lengthy test results from myself and other professionals in the coming weeks; stay tuned.]

If you’re not familiar with measuring extraction, 1 percent is a really big deal.

These results confirm that the Pergtamp is most definitely promoting a more even extraction, allowing you to either increase your extraction yield without experiencing bitterness/dryness or to achieve the same extraction yield with a coarser grind, which reduces the amount of fines, sweetening and rounding the espresso. Even if you’re not measuring extraction, you will notice an improvement in cup quality.

I conducted a small test to demonstrate the difference in extraction yield between various tamper designs. With the same grind setting, dose and beverage yield, I averaged 5 separate extractions from each of the 5 different tampers. Here’s their average extraction yields:

American Curve 58mm: 16.9%
C-curve 58mm: 16.8%
Flat 58mm: 17.5%
Flat 58.35mm: 17.8%
Pergtamp: 18.9%

Keep in mind that these are all average values taken across 5 shots. The C-curve sometimes dropped to 16%, and the 58.35mm did reach 18.2% once, but the Pergtamp never dropped below 18.7% or exceeded 19.1%. Consistency and a higher extraction are major factors in a tamper comparison.

Since VST baskets were introduced, we have been enjoying much higher and more even extractions than ever before. Amongst many other improvements, the holes of a VST basket extend much further towards the edges. Compared to almost every other basket, this significantly increases water flow around the edges. If your tamper is compressing the grinds at the edges less than the grinds in the middle, the water will find the path of least resistance and create an uneven extraction. This is why Pergtamp increases extraction yield; it treats every coffee grind the same way, and promotes a perfectly even flow of water throughout the entire bed of coffee.

Taste

In terms of taste, a more even extraction has the opportunity to be much sweeter, richer and balanced. A common struggle with espresso brewing is the compromise between pulling a longer, more dilute espresso to achieve more sweetness or pulling a shorter, stronger espresso that has a richer mouthfeel but can be sour or unbalanced. With a Pergtamp, this compromise is noticeably diminished. By increasing extraction yield with the same brewing recipe, a Barista can make espressos that are simultaneously sweeter, richer and more balanced. Triple-win.

Nutating

The Pergtamp was initially designed to aid nutation. I used version 1.0 of this tamper in the 2013 WBC, and you can see how this tamping technique works here. The tapered sides allow the tamper to be 58.55mm wide but also able to be tilted aggressively off-axis if required.

Usage

The Pergtamp is different to every other tamper you’ve ever used, and should be treated as such. Here are a few simple directions that – when followed – will result in a long-lasting relationship of compressed grinds and tasty espresso.
The Pergtamp is made with a higher grade of stainless than almost every other tamper on the market. Nevertheless, it still has a sharp edge that should be treated like a quality knife. Never place the Pergtamp on a hard surface, drop it on the floor or hit the edge against hard objects. This will eventually bend the edge, changing the diameter and resulting in a tight fit, jamming, or uneven tamping. I recommend placing the tamper on a cloth, which also helps keep the tamping surface clean and dry. This product will not be replaced due to carelessness or improper use; it is a precision instrument and should be treated as such.

Always pull the Pergtamp out of the basket slowly. Although the tapered sides increase airflow, there is still a vacuum effect if removed quickly. Watch out for any cracks appearing in the surface of the coffee grinds; this indicates that you are removing the tamper too quickly, and air is being forced up through the grinds instead of around the edges of the tamper. You will need some practice to develop a technique that works, but once it becomes habit you’ll never think about it again. I have used this tamper on busy 800-coffee days at St Ali without a single channelled shot. If you still experience channelling, ensure that you aren’t bumping the portafilter against the bench, machine or group head; most baristas don’t even notice that they’re doing this and will invariably blame the tamper.

Only use VST baskets. This tamper will not fit in or work well with any other brand of basket. You shouldn’t even be using another basket because they’re all terrible. Without exception.
If your grinds are not perfectly evenly distributed in the basket, you’re not letting the Pergtamp do its job. Your un-tamped bed of coffee grinds should look like a putting green before you even think about tamping. No holes, divets or mounds – just a perfectly flat bed of coffee with an even density. This should be the case for every single espresso you make. I prefer to use the ‘portafilter tapping’ method of distribution. I find it to be far superior to ‘Stockflething’, dosing tools and any manual movement of the grinds. This superiority extends to extraction yield, speed, cleanliness and ergonomics, but that’s a whole article in itself.

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