§ 17

Mixing ratio: from volume parts to grams on the scale

How many grams of hardener should I weigh for 600 g clear lacquer when the ratio is 2:1 by volume?

Answer: Many datasheets give mixing ratio in volume e.g. 2:1 + 10% but in the workshop you mix by weight. Varnish, hardener and thinner don't weigh the same per litre so 2:1 in volume isn't 2:1 in grams. The calculator converts the varnish you weighed out to its volume finds hardener and thinner in volume from the ratio and converts them to grams with each component's density. It also shows the error if you weigh the volume ratio directly as grams.

Formula

Lakkens volumen = vejet lak ÷ lakkens densitet

Hærder (ml) = lakkens volumen × hærderdele ÷ lakdele. Hærder (g) = ml × hærderens densitet

Thinner in the same way with thinner parts and thinner density

«+10%» usually means 10% of lacquer + hardener: at 2:1 it is 0.3 parts. Read the datasheet

Symbols and units in the formula
Symbol	Meaning	Unit
lak_g	Varnish (component A) weighed out	g
lak_dele	Volume parts varnish (e.g. 2 in 2:1)	—
haerder_dele	Volume parts hardener (e.g. 1 in 2:1)	—
fortynder_dele	Volume parts thinner (e.g. 0.3 for +10 % of 2:1)	—
rho_lak	Varnish density (datasheet)	g/ml
rho_haerder	Hardener's density (datasheet)	g/ml
rho_fortynder	Thinner density (datasheet)	g/ml
=	Hardener on the scales	g
=	Thinner on weight	g
=	Total weight ready to inject	g
=	Total volume ready to inject	ml
=	Error on the hardener if the volume ratio is weighed as grammes	g

Validity and source

Source: Forholdsregning + densitet fra produktets tekniske datablad (masse = volumen × densitet)

Does not apply when

Many mixing systems have the weight ratio ready in the programme and then you should use it. Density (specific gravity) is in the product's technical datasheet or safety datasheet, section 9.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

Varnish (component A) weighed out600 g
Volume parts varnish (e.g. 2 in 2:1)2
Volume parts hardener (e.g. 1 in 2:1)1
Volume parts thinner (e.g. 0.3 for +10 % of 2:1)0.30
Varnish density (datasheet)1.10 g/ml
Hardener's density (datasheet)1 g/ml
Thinner density (datasheet)0.88 g/ml

Giver

Hardener on the scales272.7 g
Thinner on weight72.0 g
Total weight ready to inject945 g
Total volume ready to inject900 ml
Error on the hardener if the volume ratio is weighed as grammes27.3 g

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Sådan bruger du den

Mange datablade giver blandingsforholdet i volumen, fx 2:1 + 10 %, men på værkstedet blander du på vægten. Lak, hærder og fortynder vejer forskelligt pr. liter, så 2:1 i volumen er ikke 2:1 i gram. Beregneren omsætter lakken du har vejet op, til gram hærder og fortynder med hver komponents densitet.

Step by step

Vej lakken op.
Tast volumendelene.
Tast densiteterne fra databladet.
Vej hærder og fortynder op efter tallene.

Typical errors

At veje volumenforholdet direkte.
At bruge forkert densitet.
At regne 10 % af lakken alene.

Examples from everyday life

Klarlak 2:1 + 10 %

Du vejer 600 g klarlak op. Forholdet er 2:1 + 10 % i volumen.

Varnish (component A) weighed out: 600 g
Volume parts varnish (e.g. 2 in 2:1): 2
Volume parts hardener (e.g. 1 in 2:1): 1
Volume parts thinner (e.g. 0.3 for +10 % of 2:1): 0.3
Varnish density (datasheet): 1.1 g/ml
Hardener's density (datasheet): 1 g/ml
Thinner density (datasheet): 0.88 g/ml

It means: Vej 272.7 g hærder og 72 g fortynder. Blandingen vejer 945 g og fylder 900 ml. Vejede du 2:1 som gram, ville hærderen være 27.3 g forkert.

Fyldprimer 4:1 + 10 %

Du vejer 400 g fyldprimer op. Forholdet er 4:1 + 10 %, altså 0,5 dele fortynder.

Varnish (component A) weighed out: 400 g
Volume parts varnish (e.g. 2 in 2:1): 4
Volume parts hardener (e.g. 1 in 2:1): 1
Volume parts thinner (e.g. 0.3 for +10 % of 2:1): 0.5
Varnish density (datasheet): 1.45 g/ml
Hardener's density (datasheet): 1 g/ml
Thinner density (datasheet): 0.87 g/ml

It means: Vej 69 g hærder og 30 g fortynder. Fejlen ved at veje volumenforholdet som gram ville være 31 g.

Rule of thumb

Er lakken tungere end hærderen, skal der færre gram hærder i end volumenforholdet siger.

How to check the answer

Samlet vægt ÷ samlet volumen skal ligge mellem komponenternes densiteter.