Best Way to Split a Cake? Try a Dozuki Saw.

Puerh and other heicha
Post Reply
User avatar
pedant
Admin
Posts: 1516
Joined: Fri Sep 29, 2017 4:35 am
Location: Chicago
Contact:

Sat Dec 19, 2020 12:06 am

For some time, I've been pondering the best way to split bingcha, bricks, and other compressed tea (puerh or otherwise) for sharing with friends.

Some people work it apart using an awl, like this Osborne 478 Scratch Awl (available on Amazon).

I believe @phyllsheng uses a coping saw sometimes. I've heard of people using hacksaws as well.

A good method should balance:
  • Ease of splitting
  • Minimization of waste
  • Clean appearance
With some practice and a bit of patience, an awl can be a good way to go, but it's not easy at all with tightly-compressed tea.

I like the saw approach, so I decided to search for one that makes the narrowest possible kerf.
The best I can find so far is this dozuki by Suizan:

Dozuki Saw
Dozuki Saw
dozuki-saw.jpg (133.39 KiB) Viewed 3673 times

Dozuki is a kind of Japanese woodworking saw with a thin blade supported by a stiffening spine. I think it's often used to cut delicate joints. The teeth seem made for cross cutting which is probably good for this application, but it probably doesn't matter since tea is comparatively soft material.

According to the manufacturer, this one's 8" (20cm) blade is 0.008" (0.20mm) thick and cuts a 0.012" (0.30mm) kerf. Actually, I measured 0.18mm blade thickness:

Dozuki Saw: Blade Thickness
Dozuki Saw: Blade Thickness
dozuki-blade-thickness.jpg (85.12 KiB) Viewed 3673 times

Here are my results with this new tool. It's my first time using it.

Take a look at that narrow kerf (note that the cake is about 90% sawed through). It's almost like it was cleaved by a water jet :D

Dozuki Saw: Kerf
Dozuki Saw: Kerf
dozuki-kerf.jpg (228.58 KiB) Viewed 3673 times
Dozuki Saw: Kerf Detail
Dozuki Saw: Kerf Detail
dozuki-kerf-detail.jpg (243.95 KiB) Viewed 3673 times
Bingcha Cross Section
Bingcha Cross Section
bingcha-cross-section.jpg (201.72 KiB) Viewed 3673 times

The cutting took about 5 minutes, but a lot of that time was spent getting used to the tool and trying to find a better surface to cut on. I had to flip it over and tap out the sawdust several times. I think it'll take me a minute or two next time I have to split a cake.

I made this into a little experiment to see how much waste was generated. Here are the resulting fractions after sawing:

Cake Split Fractions (Top: Intact halves, Left: Saw dust, Right: Respectable debris)
Cake Split Fractions (Top: Intact halves, Left: Saw dust, Right: Respectable debris)
split-cake-debris.jpg (235.83 KiB) Viewed 3673 times

The original cake mass was 356.8g. After sawing, the resulting halves weighed 351.9g (98.6% of the original cake!). I also recovered 3.3g (0.9%) of what I'd call respectable debris. This is perfectly usable stuff (whole leaves or large fragments, not dust), and it was generated mostly by handling the cake during splitting. Next, I collected 1.1g (0.3%) of ultrafine sawdust. I'd consider this waste, but I guess you could brew it. Finally, 0.5g (0.1%) was lost to entropy.

Cake Split Results (Dozuki Saw)
Cake Split Results (Dozuki Saw)
cake-split-results.png (11.61 KiB) Viewed 3673 times

Overall, 99.6% was recovered (98.6% in the halves!). I'm pretty satisfied with this method.

How do you guys split cakes?
karma
Posts: 160
Joined: Fri Feb 28, 2020 2:14 pm
Location: Texas

Sat Dec 19, 2020 12:16 am

Is the amount of broken leaf worth it? Every leave along the cut is now broken.

When I split a lot of cakes for a group buy, my main priority was keeping leaves whole. To do so I mostly worked cakes apart by way of tea tool and prying apart, and then working by hand. It took a lot longer than your method.
User avatar
pedant
Admin
Posts: 1516
Joined: Fri Sep 29, 2017 4:35 am
Location: Chicago
Contact:

Sat Dec 19, 2020 12:20 am

karma wrote:
Sat Dec 19, 2020 12:16 am
Is the amount of broken leaf worth it? Every leave along the cut is now broken.
good question!

so far, i think the simple answer is yes. i believe it's a good compromise of:
pedant wrote:
Sat Dec 19, 2020 12:06 am
  • Ease of splitting
  • Minimization of waste
  • Clean appearance
i reserve the right to change my mind, obviously. lol

a related question: how many broken fragments, fines, and dust are made in the pursuit of preserving leaves with an awl or pry tool? all of that handling causes breakage as well.
i think the success ceiling of your method is inversely related to the level of cake compression. that is to say that maybe for a cake with very loose compression, you can do a better job than i can with this saw. i'm a little skeptical, however.

split a cake your way and weigh the resulting fractions for us ;)

i actually want to repeat this experiment your way, but i need to find a very loose cake first to give it the best chance of quantitative success.

for a tightly compressed cake, i'd be very surprised if the saw is not the best method in every respect.
User avatar
pedant
Admin
Posts: 1516
Joined: Fri Sep 29, 2017 4:35 am
Location: Chicago
Contact:

Sat Dec 19, 2020 1:32 am

obviously measuring the dust made by carefully prying a cake in half doesn't tell the whole story (i didn't look at leaves broken by sawing), but if you end up with less dust and fines than the saw makes, that's a pretty compelling argument against the saw. at least if you aren't in a hurry.

empirically examining the broken leaf issue would be pretty painstaking on a sawed cake. maybe i could model it, though.
User avatar
Victoria
Admin
Posts: 3043
Joined: Sat Sep 30, 2017 3:33 pm
Location: Santa Monica, CA
Contact:

Sat Dec 19, 2020 2:00 am

Really nice write up and analysis. The beautiful sawn compressed tea bingcha, bricks, remind me of peat blocks formed in bogs, a type of wetland.
User avatar
Balthazar
Posts: 706
Joined: Mon Apr 02, 2018 7:04 am
Location: Oslo, Norway

Sat Dec 19, 2020 2:10 am

I don't see broken leaves as a huge issue, especially considering you did a vertical and not a horizontal split. The split came out surprisingly clean, I have to say. I'm surprised by the small amount of sawdust.

If any EU members are reading this and want to pick up a dozuki, Dieter Schmid's Fine Tools has a very reasonably priced selection.

As for myself, I'm an awl person and don't split cakes often enough to justify picking up a dozuki just for that purpose. Although I do have a heizhuan brick that is a real pain (think iron cake on steroids) to work with...
.m.
Posts: 877
Joined: Wed Oct 11, 2017 3:26 pm
Location: Prague

Sat Dec 19, 2020 3:04 am

Wow, nice. That's such a clean cut! 👏
User avatar
cbrace
Posts: 54
Joined: Wed Sep 16, 2020 9:00 am
Location: Amsterdam

Sat Dec 19, 2020 6:33 am

That cross-section is amazing! I feel like sawing one of my cakes in half just take a look :D
User avatar
Maerskian
Posts: 110
Joined: Fri Nov 15, 2019 11:41 pm
Location: Atlantis

Sat Dec 19, 2020 7:58 am

Thanks a gazillion @pedant for starting this thread and sharing everything with such amount of detail, something that takes a fair amount of time and nowadays everybody takes for granted - spoiled by a world oozing with information everywhere - but it's worth taking a nanosecond to virtualize all the steps and do the math... so thank you! ... genuinely.

As somebody that still have to improve A LOT with a regular pick, watching samples i received looking like the vendor just pulled with his bare hands barely breaking anything always shock me.

Always wondered as well about tea drinkers into trading teas which always raise some questions about the skills of each side involved although i was thinking mostly about sample-sizes, now... splitting whole cakes also has been in my mind and this thread is incredibly helpful when it comes to deal with tightly compressed "any-shape", and an amazing starting point ( given there's a better way to do it in the end ).

Remember seeing some post on reddit ( ? ) , some blog post ( ? ) ... where somebody tried using pincers with supposedly good results, although i can't even remember the compression level.

By the way, thanks @Balthazar for that link .
Post Reply