Give a couple?

We love to take a good steam bath no less than Finns and oth­er north­ern­ers, and indi­vid­ual bath­hous­es grow like mush­rooms in our sum­mer cot­tages. BUTtogeth­er with them, the demand for heaters is grow­ing, with­out which it is impos­si­ble to warm up the bath­house and pre­pare the steam that is so nec­es­sary for the cer­e­mo­ny.

SaunaSet­Spe­cial­ists unan­i­mous­ly agree that a “light”, in oth­er words, super­heat­ed steam is need­ed in a sauna. Andcom­plete­ly mis­placed fog- a sus­pen­sion of small water droplets in the air. Fog, unlike steam, makes it dif­fi­cult to breathe and can make you leave the steam room already at a “child­ish” tem­per­a­ture of 60 C. To get super­heat­ed steam, you need to heat the main vol­ume of stones up to 300 C. The “readi­ness” of the stones is deter­mined exper­i­men­tal­ly: the water spilled on them should evap­o­rate in a split sec­ond, and not boil on the sur­face. Some heaters- for exam­ple, “Geyser” (“Ter­mo­for”), “Rus”, “Sahara” (“Teplo­dar”) (both- Europe)- equipped with a con­ve­nient built-in steam gen­er­a­tor: water is poured into a spe­cial con­tain­er, and then it goes through the pipeline to the hottest stones. The inten­si­ty of steam for­ma­tion in the Rus and Sahara ovens can be adjust­ed using a valve.

life-giving flame

Mason­ry stoves in the bath are rarely erect­ed today. Andthe rea­son for this is not only the short­age of crafts­men and the high cost of their ser­vices.Most like­ly, the mason­ry oven does not meet the mod­ern rhythm of life and the idea of ​​​​sav­ing ener­gy resources. To heat a bath­house with it, even in sum­mer it takes 4–6h and 60–70kg of fire­wood. AToff-sea­son, espe­cial­ly in win­ter, a mas­sive brick struc­ture, if it is locat­ed in a sep­a­rate unheat­ed build­ing, man­ages to accu­mu­late so much cold in a week that it will take a whole day and a good pile of fire­wood to warm up on its own. ToIn addi­tion, fre­quent freez­ing / thaw­ing will great­ly reduce the life of the mason­ry (it is well known that bricks today are not at all what they were 100years ago). In addi­tion, the oven will need 300–600 bricks (15–25rub./pc.). FROMtak­ing into account the cost of work (usu­al­ly- 150% of the price of the mate­r­i­al) the con­struc­tion will cost 37,500rub. Hav­ing paid the same amount, you can buy a ready-made econ­o­my class heater with­out any has­sle. How­ev­er, we do not want the read­ers to get the impres­sion that the brick oven con­sists of only short­com­ings. She has dig­ni­ty, which in cer­tain con­di­tions out­weighs all the dis­ad­van­tages. This is the abil­i­ty to accu­mu­late heat dur­ing the fur­nace, and after its com­ple­tion for a long time (up to a day) to emit “soft” radi­a­tion, char­ac­ter­is­tic of a tra­di­tion­al Euro­pean bath.

AndNev­er­the­less, today most devel­op­ers pre­fer met­al heaters that pro­vide fast (from 40min up to 1.5h) heat­ing the room, easy to install and does not require a foun­da­tion. In addi­tion to wood, there are elec­tric and gas units on sale. They are sig­nif­i­cant­ly less pop­u­lar for sev­er­al rea­sons. Per­haps the main one is more roman­tic than prac­ti­cal. After all, with­out a live fire, with­out crack­ling logs and a light aro­ma of smoke, the bath los­es some of its charm. Well, a pure­ly prag­ma­tist will note that an elec­tric heater will cost almost 2 times more than a wood stove and will sig­nif­i­cant­ly increase elec­tric­i­ty costs. ToIn addi­tion, for the most part, such equip­ment requires a volt­age of 380C. As for gas stoves, their choice is very small, and far from all home­own­ers are pro­vid­ed with main gas (as well as three-phase cur­rent).

So, the palm belongs to fac­to­ry-made wood-burn­ing heaters. Prod­ucts from more than ten com­pa­nies are rep­re­sent­ed on our mar­ket, and even the most demand­ing cus­tomer will not have to com­plain about the pover­ty of the assort­ment. But from which end to start choos­ing “your” stove? It is pos­si­ble from the design or dimen­sions, but we rec­om­mend that you first of all decide on the pow­er of the unit.

Pho­to 2
“Teplo­dar”
Pho­to 3
ITS/Helo
Pho­to 4
ITS/Helo

1. Mod­el 20 Pro (Harvia) is equipped with a cast-iron door, and the upper wall of the fur­nace fur­nace is made of steel with a thick­ness of 10mm. Price- from 160 $.

2. Fur­nace “Rus” (“Teplo­dar”) with a steam gen­er­a­tor- from 80 $.
3. Stone-lined steel stove is safer to oper­ate

4. Mod­el 20 SL (Helo) with wall tun­nel. Price- from 210 $.

Tutelka in tyutelka

If the stove pro­duces too much heat, the air in the steam room will heat up quick­ly, but the stones will only be slight­ly warm. The bath will have to be heat­ed, con­stant­ly air­ing, that is, heat­ing the street at its own expense. But it’s still half the trou­ble. It is much worse if, after pur­chase and instal­la­tion, you find that the pow­er of the stove is insuf­fi­cient.- the tem­per­a­ture in the steam room does not want to rise above 50 C. Indeed, in this case, you will either need to addi­tion­al­ly insu­late the bath, or pur­chase a new unit- both mean the loss of a con­sid­er­able amount and the delay in the start of the “bathing sea­son”.

The pow­er of sauna stoves varies between 6–27 kW. This tech­ni­cal char­ac­ter­is­tic, as a rule, is con­tained in the prod­uct pass­port (if not- this should be checked with the man­u­fac­tur­er). There is also an indi­ca­tion of the min­i­mum and max­i­mum vol­ume of the steam room, which can be heat­ed using the device, for exam­ple 8–18m3. How­ev­er, this does not mean that the stove is equal­ly well suit­ed for all rooms with a cubic capac­i­ty that fits into this range. The man­u­fac­tur­er’s rec­om­men­da­tion should rather be read like this: the stove is suit­able for heat­ing a very poor­ly insu­lat­ed steam room with a vol­ume of 8m3 and very high qual­i­ty insu­lat­ed vol­ume 18m3. In order to assess the ther­mal insu­la­tion of the steam room and not make a mis­take with the choice of the pow­er of the device, it is bet­ter to use the table below and take into account in the cal­cu­la­tions that the glass door will require an increase in the cubic capac­i­ty of the room by 1m3and each square meter of win­dows fac­ing the street with dou­ble-glazed win­dows- on 10 %.

Expert opinion

As stones for sauna stoves, the most afford­able- peri­dotite, basalt, dia­base (cost 20kg- 300–400rub.). More beau­ti­ful and heat-inten­sive soap­stone is some­what more expen­sive- 800rub. for 20kg.The high­est price will have to be paid for green­ish semi-pre­cious jadeite (a stone sim­i­lar to jade with a fine grained struc­ture) and white quartz (also called hot ice)- up to 1400rub. for 5kg.When choos­ing stones, you should pay atten­tion to their size (it should be indi­cat­ed on the box). Opti­mal frac­tion for a small oven (up to 12 kW)- 8–12see. The stones are laid in such a way that the area of ​​​​their con­tact with the walls of the fur­nace is max­i­mum: down- larg­er and flat­ter, on top- slight­ly less. In this case, it is nec­es­sary to leave a gap between the stones for free air cir­cu­la­tion.

Andrey Slavnov, chief engi­neer of the con­struc­tion depart­ment of the Group of Com­pa­nies 95 FROM”

Fires in furnaces…

The most com­mon type of sauna stoves- steel dou­ble-walled, that is, hav­ing a fire­box and a cas­ing. Thanks to this design, the exter­nal sur­faces of the unit main­tain a safe tem­per­a­ture, and at the same time, the air cir­cu­lat­ing between the walls quick­ly warms up the room. Some Mod­els- in par­tic­u­lar, KO-20, KH-20, KT-S-20, KT-H-20 (Kas­tor, Fin­land)- equipped with an addi­tion­al inter­me­di­ate cas­ing; the tem­per­a­ture of the out­er wall of these heaters nev­er exceeds 60 FROM.

The fur­nace is made of steel sheets using elec­tric or argon-arc weld­ing. The dura­bil­i­ty of the unit depends on the thick­ness of the steel and its grade, so you should def­i­nite­ly take an inter­est in these char­ac­ter­is­tics. Heat resis­tant stain­less steels (AISI 310, 316, 321 andt.n.) with a thick­ness of at least 2.5mm or car­bon boil­ers with a thick­ness of 4–5mm. A num­ber of man­u­fac­tur­ers, includ­ing Helo (Fin­land), increase the thick­ness of the walls of the fur­nace in those places where the effect of the flame is most intense, using lin­ings up to 6mm.

A part of the fire­box is a con­tain­er for stones, built in from above or from the side,- the larg­er the area of ​​​​con­tact of stones with hot steel sur­faces, the bet­ter. The cas­ing is usu­al­ly made of half-mil­lime­ter stain­less steel or “black” steel with a thick­ness of 1–3mm and coat­ed on the out­side with heat-resis­tant enam­el.

ATMost steel fur­naces imple­ment the prin­ci­ple of grate com­bus­tion. Air is sup­plied to the fur­nace from below: it pass­es through the ajar door of the ash draw­er (or holes made in it), and then, under the influ­ence of trac­tion, rush­es upward through the slots in the grate on which the fire­wood lies. You can reg­u­late the inten­si­ty of com­bus­tion by push­ing / push­ing the ash draw­er or by manip­u­lat­ing the damper on its door. Since the grate is locat­ed in the zone of the high­est tem­per­a­tures, it must be made of cast iron. With grate com­bus­tion, it is pos­si­ble to quick­ly achieve real heat, how­ev­er, a sig­nif­i­cant part of the heat flies out into the chim­ney due to strong draft. There is anoth­er minus- even spe­cial steels, when used in such con­di­tions, are prone to the for­ma­tion of scale, and over time, the walls of the fur­nace become thin­ner. Some man­u­fac­tur­ers, in an effort to light­en and reduce the cost of their prod­ucts (with­out reduc­ing the ser­vice life), devi­ate from the clas­si­cal scheme. For exam­ple, the plant “Feringer and K” (Europe) has released a line of heaters with­out a grate- with the so-called upper igni­tion. Com­bus­tion in them takes place on the hearth, and air is sup­plied through a slot in the upper part of the fur­nace door. True, it should be not­ed that such a fur­nace heats both the room and the stones some­what more slow­ly than the grate.

Pho­to 6
ITS/Helo
Pho­to 7
Tulikivi

Struc­tur­al scheme of the heater “Ter­mo­for”:

one- hang­ing tank for water;
2- cas­ing;
3- built-in tank;
four- capac­i­ty for stones;
5- pass-through mod­ule with a door;
6- fur­nace;
7- ash box

BUTif harder?

Steel fur­nace with stone back­fill weigh­ing 20–40kg heats up quick­ly, but cools down just as quick­ly. BUTwhat if you have a large fam­i­ly or you are not averse to invit­ing guests to the “banya”? After all, then the high tem­per­a­ture in the steam room will have to be main­tained for sev­er­al hours. You can, of course, keep throw­ing fire­wood into the fire­box all the time, but this is quite trou­ble­some, and besides, you risk over­heat­ing the room. To arrange bathing days, you need a mas­sive stove that stores heat for a long time. Andnev­er­the­less, I would like it to heat up faster than a brick one, serve longer and look more attrac­tive.

One pos­si­ble solu­tion in this case- steel unit with a lat­tice cas­ing. This design is designed to fill a large mass of stones between the walls of the fur­nace and the out­er grate made of steel bars coat­ed with heat-resis­tant paint. These are, for exam­ple, the Leg­end 150, Leg­end 240 and Leg­end 300 ovens (Harvia), allow­ing to heat 120, 200 and 260 respec­tive­lykg of stones. At the same time, the mass of stones can be increased by anoth­er 20–40kg by pur­chas­ing a lat­tice fence for the first chim­ney mod­ule. (Keep in mind that a wood-topped sauna may require a foun­da­tion for such a stove!) The out­er stones don’t get too hot, mak­ing the stove quite safe, but it can store heat for at least 3h after the end of the fur­nace. The cost of devices of this type starts from 150 $.

Got­ta fresh­en up

Sup­ply and exhaust ven­ti­la­tion in the steam room is a must. First­ly, to be able to reg­u­late the humid­i­ty and tem­per­a­ture dur­ing the pro­ce­dure. Sec­ond­ly, to ven­ti­late the room after the end of the ses­sion; with­out this, wall cladding and reg­i­men­tal boards will begin to rot inten­sive­ly. Final­ly, if the fur­nace hole and the blow­er of the fur­nace go into the steam room, it will be nec­es­sary to orga­nize an influx of fresh air for com­bus­tion (but in this case there will be no need for an exhaust hood). For fresh air to enter, make a hole in the floor or wall (not high­er than 0.5m) in the cal­cu­la­tion of 5 cm² per 1m3 the vol­ume of the steam room or leave a gap 1–3see under the door leaf. The exhaust open­ing is usu­al­ly locat­ed on the ceil­ing; its cross-sec­tion­al area must cor­re­spond to the cross-sec­tion­al area of ​​the inlet. The opti­mal sys­tem will be forced exhaust ven­ti­la­tion, in which the exhaust duct is led out through the floor and sup­plied with a fan,- in this way it is pos­si­ble to con­stant­ly “pump out” the most humid and cold air from the sauna.

A num­ber of man­u­fac­tur­ers offer stoves with sawn stone lin­ing.- soap­stone. So, the com­pa­ny “Teply Kamen” (Europe) pro­duces stain­less steel fire­box­es, com­plet­ed with facade soap­stone plates and cor­ner mod­ules, which are mount­ed with­out the help of glue, insert­ed into the grooves of the hold­ers on a small (20–50mm) dis­tance from the fur­nace walls. The gap is nec­es­sary, first­ly, to com­pen­sate for the ther­mal expan­sion of the met­al. Sec­ond­ly, thanks to this solu­tion, the stove retains all the advan­tages of a dou­ble-walled design: the out­er sur­faces do not heat up, and the room almost imme­di­ate­ly after kin­dling begins to warm up with con­vec­tive air flows. Prod­ucts of the com­pa­ny “Inzhkomt­sen­tr VVD” (Europe) are sim­i­lar­ly arranged. True, they have a heav­ier cast-iron fire­box, and the out­er walls are made of rather thin tiles. The mass of stoves dressed in stone is usu­al­ly 200–400kg (a colum­nar foun­da­tion may be required), and the price starts from 600 $. ATsoap­stone cladding is also avail­able for some ser­i­al mod­els HarviaKas­tor, Helo (option cost- from 450 $, that is, a fur­nace with a capac­i­ty of 10–14 kW will cost about 60–750 $).

The most mas­sive of the fac­to­ry-made bath stoves offered on the mar­ket are assem­bly kits from soap­stone mod­ules. They are sup­plied to the domes­tic mar­ket by Tulikivi (Fin­land). Such heaters have a mass of 500kg and require a foun­da­tion. They are assem­bled on site using spe­cial glue. The grate and the fire­box door are made of cast iron. The cost of mod­u­lar ovens- from 1300$.

Pho­to 9
“Ermak-Ther­mo”
Pho­to 11
“Typhoon”
Pho­to 12
Tulikivi

9. The Leg­end mod­el has a glazed cast iron door and adjustable feet. The lat­tice cas­ing is assem­bled with dec­o­ra­tive riv­ets and coat­ed with heat-resis­tant paint. Price- from 220 $.
10. The Leg­end mod­el has a glazed cast iron door and adjustable feet. The lat­tice cas­ing is assem­bled with dec­o­ra­tive riv­ets and coat­ed with heat-resis­tant paint. Price- from 220 $.
11. The mod­el “Vesu­vius Skif” (“Typhoon”) with a pow­er of 18 kW is designed for lay­ing 180kg of stones. Price- from 150 $.
12. Mod­el SK 950 (Tulikivi) has a curb weight of 930kg, and anoth­er 130kg of stones fall asleep from above. How­ev­er, due to the large vol­ume of the fur­nace, the fur­nace warms up in just 2–3h Price- from 134 thou­sand rubles.

The issue of water supply

You can’t do with­out hot water in the bath. To wet the broom and get steam, you need quite a bit of it.- no more than 10l, but for wash­ing in the show­er it will take anoth­er 40–60l boil­ing water. For a bath with a show­er, it is best to pur­chase a stove equipped with a heat exchang­er- a small capac­i­ty built into the fur­nace and equipped with spur pipes for con­nec­tion to the DHW sys­tem. There are also spe­cial heat exchang­ers on sale that func­tion as the first chim­ney mod­ule,- by the way, they can be installed on any oven. FROMusing a heat exchang­er for 1h can be heat­ed 80–200l water up to 60 C. Every­thing would be fine, but such units can­not be heat­ed “dry”: the thin met­al of the heat exchang­er “leads” under the influ­ence of the flame, and the welds diverge. This sig­nif­i­cant­ly com­pli­cates the oper­a­tion of the stove in win­ter, because every time you have to fill the sys­tem with water (first- warm, so that the pipes do not “grab”), and at the end of the day, drain it.

If there is no soul, you will have to wash in the old fash­ioned way- right in the steam room. Then it makes sense to pur­chase a stove with a built-in or hinged (installed on a stove or chim­ney) water tank. Tank vol­ume 25–30l with eco­nom­i­cal spend­ing is enough even for a large fam­i­ly. Draw­back one- when water boils in the tank, the room is filled with sat­u­rat­ed steam, and it becomes impos­si­ble to stay in it at a high tem­per­a­ture. How­ev­er, mod­ern units with a weld­ed tank can be fired with­out water. But every time you have to choose: bathe or wash. Or heat the stove 2 times with a break, since it is impos­si­ble to pour water into a red-hot tank.

Session from a professional

Rec­om­men­da­tions of a mem­ber of the Inter­na­tion­al Asso­ci­a­tion of Bath Art Alex­ei Bely.

First stage- prepara­to­ry. Melt the stove, steam a broom an hour before the start of the pro­ce­dure (to do this, heat the water to 60 FROM; I advise you to add propo­lis infu­sion to it- 30 g per 10l). Do not for­get to boil tea or cook fruit drinks, pre­pare light veg­etable or fruit dish­es, stock up on tow­els, hats andt.e. Take a show­er imme­di­ate­ly before enter­ing the steam room.

Sec­ond phase- warm­ing up the body. The tem­per­a­ture in the steam room- about 85 C. It is bet­ter to bask in sev­er­al vis­its of 5–10min.

Third stage- inhala­tion and aro­mather­a­py. At the same tem­per­a­ture, pour clean water on the stones first (oth­er­wise the smell of burn­ing will appear), and then infu­sion of a broom, med­i­c­i­nal herbs or a solu­tion of aro­mat­ic oil (a few drops per ladle). ATwith­in 10–20min breathe heal­ing steam.

Fourth stage- soar­ing. Ven­ti­late the steam room by low­er­ing the tem­per­a­ture to 60–70 C. There is time for a cup of sweat­shop tea in the dress­ing room. After that, you can start steam­ing with a broom. First, with light move­ments, grab the steam from the ceil­ing and direct it to the body, almost with­out touch­ing it. The famil­iar “groom­ing” with a broom is appro­pri­ate only at the very end of the pro­ce­dure.

Fifth stage- final. Take a show­er and have some tea.

Around the hearth

When installing a bath stove, spe­cial atten­tion will be required to the issue of fire safe­ty. ATSniPe 41–01-2003 “Heat­ing, ven­ti­la­tion and air con­di­tion­ing” shows the min­i­mum dis­tances from the inner walls of the fur­nace and chim­ney to unpro­tect­ed com­bustible struc­tures — 500mm and up to pro­tect­ed- 380mm. How­ev­er, the doc­u­ment refers to a brick heat­ing stove. Do these stan­dards apply to mod­ern steel sauna stoves- it is dif­fi­cult to say, there­fore, when installing them, they are often guid­ed by the instruc­tions of the man­u­fac­tur­ers, in which the instal­la­tion dis­tances can vary over a fair­ly wide range (250‑1300mm) depend­ing on the pow­er and design of the prod­uct. ATIn any case, the walls and ceil­ing next to the stove are best pro­tect­ed with a heat-insu­lat­ing “sand­wich”. For exam­ple, in this way: screw a gyp­sum fiber board to the wall with self-tap­ping screws, then glue a rigid Fire­batts stone wool board (Rock­wool, inter­na­tion­al con­cern) with a thick­ness of 25, 35 or 50 to it with cement-based gluemm. The joints of the plates should be closed with alu­minum tape. Glue anoth­er lay­er of GVL on top and veneer it with arti­fi­cial or nat­ur­al stone. Anoth­er vari­ant- a lay­er of asbestos card­board and fiber-cement board LW Sauna (Miner­it, Fin­land). Some fur­nace man­u­fac­tur­ers, in par­tic­u­lar Harvia, offer spe­cial pro­tec­tive screens for cer­tain mod­els, made in the same style as the oven. Experts rec­om­mend heat­ing steel heaters before instal­la­tion on the street so that the oil that inevitably remains on the met­al after rolling burns out, and harm­ful volatile com­pounds evap­o­rate from the paint­work.

Pho­to 13
ITS/Helo
Pho­to 14
Kas­tor
Give a couple? Pho­to 15
Raab

13, 14. Soap­stone lined stoves: Hiidenkivi (Helo) (Pho­to 13)- from 760 $. and KL-20JK (Kas­tor) (Pho­to 14)- from 600 $.

AndFinal­ly- a few words about chim­neys. As a rule, sauna stoves are designed for the instal­la­tion of a mod­u­lar steel chim­ney. It is bet­ter not to save on a chim­ney, since fire safe­ty direct­ly depends on its qual­i­ty. It makes sense to pur­chase dou­ble-cir­cuit mod­ules made of stain­less steel with a lay­er of stone wool (cost 1m of pipe- from 1800rub.; price of fit­tings- from 1200rub. for 1 piece). For the pas­sage of ceil­ings and roofs, it is bet­ter to use ready-made solu­tions offered by the chim­ney man­u­fac­tur­er. Most man­u­fac­tur­ers of sauna stoves also pro­duce chim­neys. FROMon the one hand, it is not at all nec­es­sary to buy the entire set from one com­pa­ny, since the diam­e­ters of the chim­neys are stan­dard- 115 (most com­mon), 120, 130 and 140mm. FROMon the oth­er hand, it should be tak­en into account that the actu­al diam­e­ter of the pipes at the ends, due to the pecu­liar­i­ties of the exe­cu­tion of the dock­ing unit, can vary by 1–2 for dif­fer­ent com­pa­niesmm. It’s not scary if the pipe is large- the joint can be sealed with asbestos cord. Worse, if she does not want to “sit down” on the stove. There­fore, when buy­ing, it is bet­ter to have a caliper with you.

Give a couple?

Pos­si­ble com­plete set of a flue:

one- mod­ule for con­den­sate removal;
2- a tee for con­nec­tion to the heat­ing unit;

3- an arm for fas­ten­ing to a wall;
four- clean­ing;
5- clamp­ing col­lar;
6- pipes;
7- umbrel­la deflec­tor

Chim­neys made of ceram­ic pipes are very durable. In the domes­tic mar­ket, they are main­ly rep­re­sent­ed by the prod­ucts of Schiedel (Ger­many). These are mod­u­lar sys­tems, in which the inner tube is made of fired chamotte mass and has a wall thick­ness of 8mm, and the shell is made of light­weight con­crete, between them- a lay­er of basalt wool.

The dependence of the power of the furnace on the design of the walls of the bath *

Wall con­struc­tion Pow­er per 1m3 steam room vol­ume, kW
Mason­ry in one and a half bricks with­out addi­tion­al insu­la­tion 2.5
Beam 100100mm or logs with a diam­e­ter of 150–200mm with­out addi­tion­al insu­la­tion 2
Beam 150150mm or logs with a diam­e­ter of 220–300mm with­out addi­tion­al insu­la­tion 1.8
Brick or tim­ber (log) wall, insu­lat­ed with a lay­er of stone wool 50 thickmm 1.3
Same with addi­tion­al radi­ant heat insu­la­tion with alu­minum foil 1.2
Wall insu­lat­ed with a lay­er of stone wool 100 thickmm, with addi­tion­al radi­ant heat insu­la­tion with alu­minum foil 0.8
* It is assumed that the floor and walls of the room are insu­lat­ed with a lay­er of min­er­al wool at least 50mm.

The edi­tors thank the “Group of com­pa­nies 95 S”, “Inzhkomt­sen­tr VVD”, “ITS Sauna”, “Teplo­dar”, “Ter­mo­for”, “Feringer and K”, “Ermak-Ther­mo”, Only for their help in prepar­ing the mate­r­i­al.

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