IMS vs VST filters - 18g unscientific home testing!

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#1: Post by swevictor »

"Long time lurker, first-time poster" :D Seriously, I've had tremendous value for the HB forum for quite some time (thanks for that!) so I thought I'd try to give back a bit of value myself!

Anyway - I've long been wondering about the difference between VST and IMS baskets. I've been reading quite a bit, but there aren't really that many comparisons out there as it seems. Thought I'd share some thoughts. The thoughts are based on quick, quite unscientific thoughts from an amateur home barista with quite a few years of experience with first Gaggia Classic and then a few E61 machines. I'll try to make as fair comparisons as possible over a few weeks. The first one completed today!

Filter baskets tested (both a few years old, bought new by me, but used in different places). Tracking down the specs (below) I realize the IMS filter might be intended for a slightly lower dose than the VST. Both were bought with an 18g dose in mind and are very similar in size, just noting.
- VST 18g, ridgeless, VST-183050r
- IMS 12-18g, 24,5mm hight ridged, B702Th24,5M, Lotto 131

The VST has an obviously larger perforated diameter, it is also flatter and has a smaller radius from the edge to the bottom.
The IMS has a smaller perforated diameter and a much larger radius from the edge to the bottom. The bottom itself is very slightly curved.
Both are very shiny and hard to photograph :)

VST left, IMS right:

Other gear
- ECM Mechanica IV Profi (E61)
- Niche Zero
- Brewista 0.1g scale
- BT-wedge-like Chinese distibution tool
- Reg Barber 58mm euro curve
- Cafelat tamping stand

- Measure 18g beans, +/- 0.1g
- Grind into Niche cup
- Shake
- Transfer to portafilter, inserted in bottomless handle
- Shake/tap to level bed
- Distribute using tool
- Tamp (not very hard)

Espresso notes will follow, please chime in regarding the above or if you have experience with both brands!



#2: Post by swevictor »

First unscientific test!

- Coffee: Nordic roasters "SOL". Mediun-light with "fruity, fresh summery" notes
- 18g +/- 0.1 coffee
- 30 seconds extraction after first drop
- Goal yield 36g


Very similar extractions (time/yield). Both filters yielded 36g +/- 1g in 30 seconds, not significant with regards to manually timing and stopping flow.

The pull
VST extraction started slightly earlier around the edge, but wet through entire basket before first drop left the filter. Espresso flow centered to one stream after 5-10 seconds and moved around the base of the filter quite a bit (not centered all the time). No striping.

IMS extraction started slightly earlier along one edge, but wet through the entire basket before the first drop left the filter. Espresso flow emerged almost directly in one, centered, stream. Slight tiger striping.

Crema / looks
No real difference. Quite a good crema initially, but disappeared relatively quickly. I would say this mostly is due to the coffee used, which never for me has provided any abundance of crema.

Shots pulled within 1-2 minutes of each other and tasted a few times while cooling. Quite similar in taste, but a slight advantage for VST which packed a bit more punch/body. Both shots were a bit too acidic for my taste, but not overly so. I typically pre-infuse this coffee to lessen the acidity, but wanted to keep the process here as similar as possible.

For me, the main takeaway so far is that the IMS filter is a bit more forgiving during the pull, but that the VMS filter might have a slight taste advantage.

The "forgiveness factor" of IMS, and that the pull looks better, is something I have noticed before and that I'm quite certain of. I theorize that the looks (centering of stream / tiger striping) are mainly due to the slightly curved base of the IMS filter. This and the smaller perforated area probably both help in the forgiveness department.

The taste is the most important part for me, by one where I don't have a strong opinion yet. In this first formal comparison, I give a slight edge to VST, but so far I'm leaning towards that they are slightly different rather than better/worse.

Any thoughts or own experiences so far?


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#3: Post by dexavator »

I have both an think VST is better when you need a finer grind with the same dose (very acidic coffee) and IMS for "normal" medium/medium low acidity. The fimer grind will tame acidity and provide more body but can cause bitterness with darker roasted coffee.


Also Victor (another Victor would create copyright issues with Another Jim :D )


#4: Post by swevictor »

Nice timing!

Coincidentally just poured a second comparison. 17g in, 34-36g out. Slightly finer grind, but no difference between the two.

VST pulled in 25 seconds, IMS filter in 30. Both well centered this time and similarly lightly zebra striped.

Both slightly less acidic with smaller and finer dose.

Very little taste difference this time, admittedly only tasted very quickly just after pulled. Then they ended up in an americano for the wife and a cappuccino for me.

Takeaway 2: I really don't like ridged filters when switching around or cleaning :lol:



#5: Post by swevictor »

So - I've been doing some more testing. Bought a larger batch of cheaper dark roast coffee to test around with. Maybe not the best idea since the fully extracted 18g shots were basically undrinkable :D

Anyhow - lowered the dose to 15g with shorter extraction times (~34g out in ~20s) which took the edge off, finally landed on 16g in, 34g out, 27 seconds as a nice in-between.

With good prep it really produces a nice pour, as well as very good flavors in the cup. Ground to match recipe above (16g => 34g, 27s)

IMS, same grind
With same prep as the VST this lower dose makes differences between the baskets show. IMS took 34 seconds to extract the same volume (16g => 34g, 34s). Not at all as nice flavors, harsher, more bitter, less crema. Not a coffee suitable for ristretto-like pours IMHO. Lower dose: Grind setting really needs to be adjusted going from VST to IMS!

IMS, coarser grind
With prep suitable for IMS (grind setting 10 => 12 on Niche Zero) i matched the VST recipe (16g => 34g, 27s). Slight doughnut extraction. MUCH better than the previous IMS. Possibly lacking a little bit of depth compared to the VST pull but very close. Actually I think this might be my prep that was a bit worse than something to blame on IMS.

- Better extraction in VST, probably due to better prep
- IMS not that much more forgiving than VST as it seems, slight doughnut tendency. Lower dose for sure makes prep harder :)



#6: Post by kidloco »

Here is my modus operandi, I have both baskets 18gr IMS and VST.

IMS anything that needs doses below 17 grams. So if I want 15gr for my very lightly roasted Ethiopia I will grab IMS. I need 17+ for Guatemala or Brasil I will go for VST. Have nothing to back this up just my "feeling", and the fact that I was pushing my light African coffees to 18gr VST for a long time but they were often too aggressive.


#7: Post by swevictor »

Sounds reasonable, I'm leaning towards IMS takes the edge of also...

So... VST saves money in the long run due to lower dose for same punch? :wink:

Just pulled a nice IMS shot ... aaand a 20s gusher on VST due to forgetting to change grind... This testing thing is hard! (ridged IMS is still annoying since the ridge catches grinds btw)



#8: Post by brianl »

Thanks for your work. I very often read that the VST struggles with dark roasts, so its interesting to see your take.

I have a VST and mostly use it for what I consider light roasts. Everything else tends to go in the standard E61 generic basket. Mostly do to my thinking that a dark roast should be high dose/coarse. Then again, when redbird was in it's hayday on the forum, many people seemed to use the VST and its definitely a darker roast.

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#9: Post by another_jim »

You may want to note that the IMS is a 12 to 18 gram basket, and if you need to grind finer for full extraction, you can simply dose lower. Out of range doses in a VST baskets are tricky; and if you want to move to a finer grind, you need to buy the 15 gram basket as well.

Anyone who believes that 18 grams is the one true dose, should use VST baskets. Otherwise ....
Jim Schulman


#10: Post by swevictor »

Absolutely. I'm a bit surprised actually that it's reasonably doable to dose 15g in the VST basket as well though. I havent tried 12g yet though :)