Cooking with Njall: Burn Baby Burn! Salt-Burn, Anyhow.

As you will remember, I’ve been screwing around with Viking-era salt production methodology. Based on a review of the language and literature, scant archaeological evidence, and good ol’ fashioned guesswork, I’ve been cobbling together a method that involves steeping kelp ashes in water in order to extract their mineral essence. That link back there is proof-of-concept. It can work, at least in principle. Cool, right?As a scientist, I’m never satisfied with an answer. Ever. It’s kind of like the Creator’s Curse, in a way – in the process of investigating a hypothesis, we learn things that often cause us to alter our understanding of that hypothesis. Rarely are you “right” at the outset. More often than not, you’ll be confronted with how the magnitude of how little you actually knew at the beginning – because you’ve gained knowledge in the process.
So we’re doomed to keep asking questions about things we’ve already investigated over and over again, because dammit we just keep learning new things.
Knowing that it’s possible simply isn’t enough. I need to know how well the method works. Is it actually feasible at a production level? Would it make sense from a fuel consumption standpoint? How hard is it to pull off? What kind of product is left behind? These are all things that we can investigate through experimentation and review, and that’s what I’m starting on here. Investigation! Skeptical inquiry! Lighting shit on fire! All the best aspects of science!
Bro, do you even science?

Bro, do you even science?

In order to investigate plausible extraction methodology, I wanted to test two different factors: water source and heat of extraction. Previously, I simply soaked charred kelp in room-temperature water and boiled the runoff. That’s great, but we also know that the solute holding capacity of water increases with temperature – so hypothetically, a hot water extraction should allow more salts to dissolve than a room-temperature one.

I also used water from my tap, which is all good and well – but this is a utility endeavor, and it was practiced on beaches isolated from major population centers. Would a salt-karl really haul fresh water from somewhere just to make salt, or would he use the seawater that’s right next to his setup? Remember, Pliny indicates that many cultures (including various Germanic tribes) made salt by evaporating seawater, and some by pouring it over the hot coals of wood. It’s plausible that seawater plus ashed kelp could be used to produce a salt; Atlantic seawater is only 3.5% salt in composition, and the saturation point for a saltwater solution is around 26% (barring any hypersaline water oddities).

Before I could do anything, though, I needed to burn some shit.

FIRE BAD

For a dude who writes about Viking stuff, you’d think I’d have more pictures of things on fire.

As I’ve mentioned before, I bought 50 pounds of Icelandic kelp meal some time ago. Since then, I’ve been trying to figure out a way to effectively burn the stuff. The configuration makes it useless as a fuel item; a friend had suggested burning it as food, and even offered up the above-pictured Lodge cookware for it. The test-run many moons ago was successful but stinky – I figured my 60,000 BTU propane burner could get the job done.

Man, did it ever. My previous efforts never resulted in significant combustion, but this stuff really took off after the initial heavy smoke phase. Interestingly enough, it also burned out and never re-ignited; my guess is that most of the carbon content burned off, leaving behind mostly mineral salts. The fire itself produced a fairly noxious-smelling black smoke, with a chewy oily texture.

Let me just reiterate how awful this shit smells. It’s extremely smokey, takes a while to burn off (I think the pot above smoked for 45 solid minutes before catching fire), and smells like a rotting whale carcass stuffed with fermented shark that is also on fire. Also the whale is on fire. Also the entire ocean is on fire.

It’s really not pleasant.

Seems there’s a good reason that “salt-karl” was an insult, and why the Norse did this on a beach well away from other people. When I came in after 3 hours of burning stuff (during which I reduced 12 lbs of kelp to ~5 lbs of ash), my fiancee could only say “UGH. What’s that smell?” And today, two days later, my peacoat still reeks.

A Sunny Day

You could smell it at the porch, and 1/4 mile into the woods down our walking path. Also STANDING NEXT TO IT FOR 3 HOURS.
Man, if only we could BUY salt or something.

So after I finished standing outside freezing my ass off while inhaling fumes of unknown toxicity, I had a tub of charred stuff that smelled fairly awful. It needed to cool overnight before it could really be useful – ashes tend to stay warm for some time. They never fully ashed, not even when combusted – but again, I believe that to be a byproduct of the configuration. Future experiments will look at trying to use sheet kelp as an actual fuel source, rather than expending heating fuel to make ashes.

Once you’ve got cooled kelp ash, it’s time to extract the mineral content! I’m used water as an extraction medium, and tried both conventional tapwater and a seawater analogue consisting of 3.5% salt.

Charred Kelp AshBoiling Water The Setup

It’s always prudent to assemble your materials before you proceed with an experiment. Here, I’ve procured my kelp ashes (~2.35 kg), propane burner and propane (set to 50% maximum output), several measuring containers, a strainer and bowl, and of course a kitchen scale.

The faux seawater solution was prepared by combining 5 kg of tapwater with 175 g of kosher salt, giving a final salt concentration of ~3.5%. Note that I weighed the water as opposed to measuring volumetrically – that’s because water has a density of 1 gm/cm^3 (until it gets near freezing, at least), so that 1 gram = 1 mL and 1 kg = 1 L. Convenient! My scale has better resolution (minimum 1 g) than my volume equipment, so this will allow for maximum accuracy.

Controls are crucial in any experiment, and it’s important to identify needed controls at the outset of an experiment – let your hypothesis govern the choices. In this case, I’m specifically looking to assess the difference in extraction efficiencies between 1) salt and fresh water and 2) low-temperature and high-temperature extractions. Because I will ultimately be measuring a mass of solid product, it’s important to know what will be contributing solids to the extracts. In order to provide controls, I boiled down 1.5 kg each of tap water and “seawater” and measured the mass of residue that could be removed from the pan.

Hard Water Residue Saltwater Aftermath

On the left, you can see the residue remaining from boiling off tapwater. We’ve got hard water here (perfect for brewing), so it’s not surprising that there is a scale left on the pan. However, it proved to be too little to effectively harvest or measure, failing to register any mass on my scale. Thus, 1.5 kg tapwater contributes less than 0.5 grams of solids to final counts. On the right, we see the residue of the “seawater,” representing the base contribution to the method as well as accounting for the losses that invariably occur when trying to harvest the salt.

1.5 kg of saltwater with a concentration of 3.5% salt by weight yielded a final salt load of 46 grams. Hypothetical yield was 52 grams, but some salt was lost in processing. Still a fairly efficient extraction. The salt was initially rather wet after drying – something like 70 grams and a consistency not unlike brown sugar – but it was heated in the microwave for 1 minute to fully dry.

For sample setup, I basically drew a Punnet square and did the appropriate combinations. 4 500-gram portions of kelp were measured into appropriately-labeled dry containers. 1.5 kg of either salt or fresh water was added to each sample. Two of the samples (one fresh and one sea) were left to steep at room temperature for 30 minutes, while the other two samples (fresh and sea) were heated in a pot on the kitchen stove. Heated samples were brought to a visible boil, and dropped to a simmer for 5 minutes after the first bubbles breached the surface. Following all extractions (whether heated or room temperature), the water/kelp masses were strained through a wire mesh strainer, and the liquid phase collected. The kelp mass was allowed to drain for 5 minutes, ensuring collection of a significant portion of the liquid.

Steeping Kelp Hot Water ExtractionDraining the Stuff

I didn’t measure the volume of runoff from each (though now I’m wishing I had) since I was only focusing on final solid extract generated by the methodology. However, all 4 extract methods appeared to produce roughly the same volume of runoff – roughly 400 – 500 mL. Future experiments will more accurately determine runoff volume generated by these extraction methods.

Once extracts were obtained, they were boiled down as the controls were. The pan was washed and dried in between each boiling (actually, all common equipment was thoroughly cleaned and dried in between samples to eliminate the possibility of cross-contamination), and the same equipment was used to extract the salt from the pan (i.e. a spoon and a spatula). Extract mass was determined using the same scale used to measure all of the ingredients. In order to standardize the moisture level, all samples were microwaved for 1 minute after collection as the saltwater control was.

KRF The Aftermath KRS The Aftermath

KHF The Aftermath KHS Aftermath

I devised an abbreviation scheme to represent the four sample configurations. All samples are identified by three consecutive letters indicating their combination of treatments: K/[R or H]/[F or S], indicating [K]elp, [R]oom-temperature or [H]igh-temperature extraction, and [F]resh or [S]altwater extraction. Top row from left to right shows the solids extracted from KRF and KRS; bottom row from left to right shows extracts of KHF and KHS.

Yields for all samples and controls are given below. Compounded uncertainty in measurements is +/- 1.5 g; the scale has no listed uncertainty of its own, and 10 consecutive weighings of identical volumes showed no deviation. Uncertainty is thus half the value of the smallest unit of measure (1 g), added for each step that involves weighing. In this case, 3 different weighings of different components were used to determine the components of the extraction process – their uncertainties add together.

Sample Name                            Mass of Extract (+/- 1.5 g)

Saltwater control                     46 g

Freshwater Control               <0.5 g

KRF                                            42 g

KRS                                            112 g

KHF                                            90 g

KHS                                           120 g

The results are not terribly surprising. Both of the hot water extractions yield more salt content than the lower-temperature extractions. The difference is greatest when using fresh water for the extraction, which indicates that the charred kelp contains quite a lot of salt to potentially extract. It is curious that the yield from KRS is larger than [KRF + Saltwater]; one would expect that the yield would simply be additive and thus the two would be mostly equivalent.

It appears that the high-temperature extraction with salt water yields the largest quantity of salt, but the gain from heating is minimal compared to a simple room-temperature salt water extraction. It appears that the use of salt water for extracting leads to the greatest gains in salt yield. This is unsurprising, as the salt water contributes a significant salt portion. It may be that the addition of charred kelp to salt water allows the solution to approach saturation; assuming 500 mL of final volume, the KHS solution would have had a solute concentration of ~24% prior to boiling.

Recovery efficiency seems to decrease as final salt mass increases. When evaporating KHS, several larger globs of salt “popped” out of the pan in response to heating. This phenomenon was observed in other extracts, and is generally exacerbated as the amount of salt condensing increases. This may also account for the observed decrease in effectiveness of heating in extracting additional salt from the kelp.

Ultimately, this demonstrates the utility of using kelp ash to increase salt yield from boiling seawater. 1.5 kg of seawater, when boiled off, yields 46 g of salt. The addition of kelp ashes to that same mass of seawater, while reducing final liquid volume, can increase the final salt yield by a factor of approximately 2.5, for a maximum yield of 120 g. This has the potential to consume less fuel (boiling a smaller volume of liquid) while simultaneously increasing salt yield.

It should be noted that expending fuel specifically to ash the kelp is likely a fuel-losing prospect. More than likely, sheets of dried kelp were themselves burned as a fuel source, and the ashes collected and used for various home purposes.

So what’s next? Fuel consumption estimation, liquid extract volume yields, experimenting with sheet kelp as fuel, additional experiments for the sake of rigor…

But before that, I’m a Norwegian, and I have salt. Let’s get some cod and see what happens when I apply kelp-ash salt to it. Next time, we’ll see how that works out.

Final Products

Seriously guys, just buy your salt. It’s way cheaper and your clothes won’t smell like a terrible tragedy at the docks.

EDIT: UPDATE WITH TOXIC METALS ANALYSIS INFORMATION

Element symbol: amount (ppb)
Note: BDL = Below Detection Limit
1 PPB = 1 ug/kg

Kelp Salt

Be: BDL
Al: BDL
V: 386.0
Cr: 491.6
Co: 180.0
Ni: 342.2
As (total): 574.2
Se: BDL
Mo: 913.8
Cd: 186.3
Sb: BDL
Hg: BDL
Ti: BDL
Pb: BDL
Th: BDL
U238: 96.01

Control Salt (Kosher Salt boiled in a pan)

Be: BDL
Al: BDL
V: BDL
Cr: 361.6
Co: BDL
Ni: 225.6
As (total): BDL
Se: BDL
Mo: BDL
Cd: BDL
Sb: BDL
Hg: BDL
Ti: BDL
Pb: 79.08
Th: BDL
U238: BDL

The arsenic (As) level was not speciated, as it was not considered a level of general concern for salt.

The FDA sets a level of concern for arsenic in juice of 23 ppb, at which point the arsenic must be speciated. Inorganic arsenic in juice has a tolerance level of 10 ppb.

The US does not set an arsenic standard for any other product.

Codex Alimentarius maintains internationally-recognized standards for contaminants in some products:

http://www.codexalimentarius.net/input/download/standards/17/CXS_193e.pdf

The standard for food grade salt is 500 ppb total arsenic, so this slightly exceeds that. However, they also note that marine products (seafood and kelp) routinely have higher levels of arsenic (mostly organic, with ~1 – 3% as inorganic), often up to 50 mg/kg (50,000 ppb).

A 2007 study by Amster et al raised some concern about arsenic in kelp supplements, but was highly criticized because it failed to speciate the arsenic, and thus could not demonstrate the toxic link it claimed. The paper also suffered other severe methodological flaws.

In general, the amount of arsenic observed in the salt is not of concern. 10 g of the salt (twice the RDA for sodium) would contain 5 ug of arsenic, well within the typical human daily consumption range. And it is unlikely that all of the arsenic is inorganic – most is likely the organic (non-toxic) form, rendering the salt largely non-toxic.

But I would not use this salt as a day-to-day table salt, to be on the safe side. As a preservative for fish which is likely to be soaked out, it should be fine.

Thanks to Tom King and the chemistry division of the NYS Department of Agriculture and Markets Food Lab!

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Cooking with Njall: Salt Burning, Take Two

A while back, I discussed a failed experiment in Viking-era salt production. The idea was to burn some Icelandic kelp, and use the residue as a “salt” of a sort. It didn’t really seem to do anything, and so I moved on.

But I’ve never been the type to just leave something alone. I’m a scientist, after all – I can’t accept that something is a bad idea until I’ve done it at least 5 times.

Rigor is very important.

I’ve had the remnants of my experiment kicking around in a Mason jar for a while now, so I figured what the hell – let’s give this another go. Refine the technique and try something new.

Salt Experiment Redux 1

I promise I am not making explosives.
Probably.

We were recently down in North Carolina visiting some of my fiancee’s friends (fellow SCA types), and Solvarr gave me a fantastic idea: do a water extraction of the charred crap, and boil that.

In the picture above, I’ve mixed 50 g of charred kelp with 100 g of water, and allowed it to steep for ~30 minutes. The idea is to attempt to extract the salts from the solid phase, separate the liquid, and boil it down to solids.

This seems like something that may have plausibly been done in the Viking era, albeit with fairly different equipment. Recall the various bits of language revolving around “salt” in Old Norse: salt-brenna (“salt-burning”), salt-fjara (“salt-beach”), and salt-ketill (“salt-kettle”). We also see words referring to two different colors of salt: hvíta-salt (“white salt”) and svarta-salt (“black salt”).

The “salt-ketill” was something I hadn’t explored before, but it makes some sense. Ash or char the kelp in a kettle (potash anyone?), mix it with water, strain out the solids (maybe with an open-weave cloth of some kind), and boil the hell out of it. Pliny makes mention of boiling seawater, and this technique is also alluded to later by Olaus Magnus, so there seems to be precedent for the generation of salt by boiling water. Adding kelp ashes would effectively increase the solute concentration, which would in turn improve yield (making better use of precious fuel).

A relatively recent excavation of a Viking-age house in Iceland (paper courtesy of Hrefna) shows an area of high salt concentration in the house. The authors suggest it to be an area used to store kelp ash – they suggest for wool dying, but of course, they could have other uses. It does show that Vikings may have generated and stored ashed and/or charred sea plants for various uses – so mixing some with water to boil into salt seems completely feasible.

Salt Experiment Redux 2

Continuing the fine tradition of putting weird things in my mouth.

After steeping, I strained the stuff through a coffee filter and squeezed the crap out of it. All in all, it generated 42 grams of the above-pictured black liquid. I lack proper volumetric measuring equipment, so I can’t effectively estimate the density of the liquid. No matter – I’m going to boil the crap away and weigh the solids. Into the pan it went, and onto the stove:

Salt Experiment Redux 3

I’m pretty sure I belong on a watch list somewhere.
Still not making explosives.

Holy crap, it worked! I got…stuff! Stuck to my pan! My fancy copper-core frying pan that cost more than I’d like to admit!

Note to self: in the future, use a cheaper pan.

This process didn’t smell nearly as badly as the initial charring experiment did. There was something of an off odor, but that was mostly due to dirty electric stove coils – though there was a hint of kelp in the air.

I scraped the solid crap into a bowl for display purposes. It was a mostly-dry salt, with a bit of residual moisture (think fleur de sel or other hand-harvested sea salt) and a variety of colors. There was some fine grey ash mixed in as well, indicating a fairly complete combustion. We likely did completely combust the kelp during the charring – we just couldn’t separate the ash from the remnant matrix.

Salt Experiment Redux 4

Right? Almost like I planned for this to happen.

After all was said and done, I had ~5 grams of that stuff up above left. So from 150 grams (50 grams kelp/100 grams water) to 42 grams liquid to 5 grams solid. Given that the kelp meal itself is 10% salt by weight, this seems like a pretty efficient extraction method! 50 grams go in, 5 grams come out. Not too shabby, doubly considering the small quantities in use.

As is tradition, the ultimate test lay in putting that shit in my mouth.

My friends, I made salt.

There’s a hint of kelp and something burned, but no real grit. Fairly crystalline texture and appearance. Very salty. Complex tasting, too – like an interesting sea salt. No funky aroma – just a hint of burnt nothingness.

It worked. Kelp ashes + water + fire = salt.

This is not the only method I tried tonight: I also attempted a different manner of direct-fire burning. I’d bought some metal mesh screen material, and this time tried building a fire underneath the charred kelp, figuring that increased oxygen flow would do the trick.

Nope.

Salt Experiment Redux 5

Also not making drugs. Or explosives.
Or salt.

I tried several configurations (the tin can there was used as a chimney starter and to try to contain the heat), but to no avail. I got the damn stuff glowing like charcoal, gave it lots of oxygen, stirred it around, left it alone, dumped lighter fluid on it – nothing.

Charred kelp meal is evidently the most flame-retardant substance known to man.

This is probably a byproduct of the configuration of the kelp – it just will not conduct oxygen and heat in such a way as to promote combustion. I’m sure that sheet kelp would actually combust like fuel – but they may very well have still mixed the ashes with water to produce the salt, as that is a good way to separate the gritty crap from the useful salt.

So my proposed method for salt production involves:

1) Charring or ashing kelp

2) Mixing that product with water

3) Separating the solids

4) Boiling the remaining liquid until only a residue remains

I have yet to experiment with actually using the stuff like salt – but at least now I have a process that will allow me to get rid of my remaining 50 pounds of kelp meal!

Future experiments will involves meat curing and fish salting using this product, to see what properties it would impart on the food. Salt is, after all, fairly fundamental in food chemistry, and the exact type of salt used can radically alter a product.

Different kettle materials can also affect the product. Iron pots, for example, will leach iron into the final salt – affecting the chemistry and flavor of any food made with it, and the diet of those who ate it.

——————————————————————————————————————

Of course, this all assumes that they were even using salt for food preservation. A redditor from the Faroe islands posted some pictures of traditional Faroese fermented lamb (skerpikjøt, which literally means “sharp meat”) over in /r/meat:

Fuck it, you win.

They slaughter the lambs in October, hang them up in a shed for a couple of months, and then eat them. Mind you, the average temperature in the Faroes at this time ranges from 4 – 8 C, so the whole place is basically a giant refrigerator. No salt, just the breeze from the North Sea blowing through the shed constantly. Air-dried and mold-covered. And they eat the stuff raw, like prosciutto but with more microbial action. It also has a very very strong gamey flavor.

My ancestors ate some weird shit, man.

Hell, they still do.

So that’s what’s in store for this series: weird-ass foods, which will eventually be coupled with weird-ass beers.

You know you love it.