· 3 min read
Salting Pasta Water Raises the Boiling Point by Two Tenths of a Degree
Fifty grams of salt in five litres is 0.171 mol/kg and buys +0.175 °C. Reaching a full degree would take 285 grams — most of a box.
Marco Bianchi
Home, DIY & motoring writer at OneKitly
Renovation, materials, measurements and the cost of running a car
Marco covers home improvement from the first measurement to the final coat, and the same arithmetic applied to a car: fuel and running costs, tyre and gear ratios, what depreciation actually takes each year. Practical guides on materials, costs and getting quantities right the first time.
Expertise
- Renovation
- Materials
- Quantities & measuring
- Car running costs
- Home energy
Track record
- Writing since 2014
- 171 guides published on OneKitly
- 93 of them on everyday
- 448 sources cited
- from 179 distinct publishers
- Publishing on OneKitly since June 12, 2025
How Marco works
Marco works from manufacturer data sheets and the trade standards a job is actually signed off against, and states the assumption behind every quantity — the waste allowance, the coat thickness, the annual mileage — so a reader can re-run the sum on their own figures instead of taking his on trust.
Articles by Marco Bianchi
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Subjects
Guides published under this byline in each section. Each link opens the section in full, across all writers.
Latest publications
· 4 min read
A Kitchen Scale and a Jug Tell You If That Tap Is Really Brass
Weigh it, sink it in water, divide. 340 g displacing 40 cm³ is 8.5 g/cm³ and brass; 272 g in the same 40 cm³ is 6.8 and a zinc casting wearing brass plate.
· 4 min read
A Stiletto Heel Presses Forty-Eight Times Harder Than an Elephant
A 60 kg person on one square centimetre of heel exerts 5.89 MPa. A five-tonne elephant on four feet of 0.1 m² each exerts 123 kPa. Same physics, opposite areas.
· 3 min read
Hardened Steel Is No Stiffer Than Mild Steel
A 10 mm² steel bar 2 m long stretches 1 mm under 1,000 N: 200 GPa. The same bar in aluminium stretches 2.86 mm and in softwood 20 mm. Heat treatment changes none of it.
· 4 min read
Carrying a Load Across a Room Is Zero Work
Push with 50 N over 4 m and you have done 200 joules. Do it in two seconds and that is 100 watts; in twenty, 10 watts — the same work at a tenth of the power.
· 4 min read
Cornering Twice as Fast Needs Four Times the Grip
A 1,500 kg car on a 50-metre bend needs 5,880 N of sideways force at 14 m/s and 23,520 N at 28. Halving the radius instead only doubles it.
· 3 min read
A Conversion Factor Has to Be Cubed
A patch 12 ft by 10 ft at 4 in deep is 40 cubic feet, which is 1.48 cubic yards — dividing by 27, not by 3. The same trap in metric is dividing by 100 where a million belongs.
· 4 min read
The Railings and Steps Are Two Fifths of a Deck to Stain
A 20 by 16 foot deck is 320 square feet of floor. Add 40 feet of railing and four steps and the surface to cover is 544 — the parts nobody counts are 41 % of the job.
· 4 min read
The Waste Allowance Is Free When the Pallet Is Big Enough
A 12 by 7.5 metre lawn is 90 m², or 94.5 with a 5 % allowance. That allowance adds eighteen slabs, five rolls — and no pallets at all, because three cover both.
· 3 min read
Twice as Wide Holds Four Times as Much; Twice as Tall Holds Twice
A cylinder of radius 5 and height 10 holds 785.4 units of volume. Double the radius and it holds 3,141.6; double the height instead and it holds 1,570.8.
· 3 min read
Why Salt Beats Sugar on an Icy Path
One mole per kilogram of a salt that splits in two lowers water's freezing point by 3.72 °C. The same amount of something that stays whole manages 1.86 °C — exactly half.
· 3 min read
Three Painters Take Twelve Days; Five Do Not Take Twenty
The rule of three turns 3 → 12 into 5 → 20, and that is right for anything that scales up together. For workers and days it is exactly backwards: the answer is 7.2.
· 3 min read
A Steeper Roof Does Not Catch More Rain
100 m² of roof under 50 mm of rain yields 4,500 litres. The area to enter is the footprint, not the sloping surface — and the 10 % missing is water the roof never delivers.
· 3 min read
Friction Does Not Care How Big the Contact Patch Is
A coefficient of 0.3 against a normal force of 100 N gives 30 N of friction, and the area never enters the formula. What does enter it, and is usually got wrong, is the normal force.
· 3 min read
Ten Metres of Copper Pipe Grows Eight Millimetres
A straight run of copper going from 20 to 70 degrees gains 8.5 mm over ten metres. Steel gains 6 mm, and a 100-metre steel span over a 60-degree year moves 72 mm.
· 3 min read
One Lux Figure for a Whole Room Is a Starting Point, Not a Plan
A 20 m² living room at 200 lux needs 4,000 lumens, or five 800-lumen bulbs. Apply a kitchen worktop's 500 lux to the same floor and it asks for thirteen — which is the moment to stop lighting rooms and start lighting tasks.
· 3 min read
The Bulb Worth Changing Is the One That Is On
Ten 60 W bulbs on five hours a day cost 219 a year; the same ten in 9 W LED cost 32.85, a saving of 186.15. Cut the hours to one and the saving falls to 37.23 — the hours matter more than the wattage.
· 3 min read
Batching Cocktails: the Water You Forgot to Buy
24 servings of 120 ml is 2,880 ml, or 2.88 litres. That is the volume in the glass, not the volume of ingredients — and the gap between the two is the reason batched drinks taste harsh.
· 3 min read
Sow Forty-One Seeds to Get Thirty Plants
82 seedlings from 100 seeds is an 82 % germination rate. Wanting 30 plants with a 10 % margin means sowing 41 — and the packet's percentage is not the one your windowsill will deliver.
· 3 min read
Cost per Serving: the Division Is Easy, the Two Numbers Are Guesses
48 divided by 6 servings is 8. Neither the 48 nor the 6 is usually right, and the two errors push in opposite directions without cancelling.
· 4 min read
Printing A4 on Letter Shrinks It to 94 %
A4 and US Letter differ by 5.9 mm one way and 17.6 mm the other, so "fit to page" scales the whole document to 94 %. Ten-point type becomes 9.4, and a plan drawn to scale is wrong by six per cent.
· 5 min read
Bar Spacing Is the Cage Rule That Actually Matters
A budgie needs bars 10 to 13 mm apart and a macaw 25 to 38. Put the budgie in the macaw cage and it can get its head through — the size is a welfare question, the spacing is a safety one.
· 5 min read
Hay by Body Weight: Flakes, Bales and a Whole Winter
A 500 kg horse at maintenance eats 10 kg of hay a day — four and a third flakes, fifteen bales a month, ninety bales across a hundred-and-eighty-day winter. The activity percentage moves that by nearly half.
· 5 min read
The 80/10/5/5 Raw Ration, Worked From Body Weight
A 25 kg dog at maintenance eats 625 g a day: 500 g muscle meat, 63 g edible bone, 31 g liver and 31 g other organ. The percentage you pick is worth more than every other input combined — growth is exactly double maintenance.