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What type of sprayer is needed?

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asked Apr 29, 2018 in Technical by anonymous

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Spraying EPDM Liquid Rubber®

Liquid Rubber can be sprayed using airless equipment. Choosing the proper equipment, however is key to achieving satisfactory results. The fluid characteristics of Liquid Rubber produce considerable pressure drop in the hose so pump size hose diameter and total length of hose must be chosen carefully in order to achieve satisfactory results.

The following recommendation is for Graco equipment. Other manufacturers with comparable pumps may also be used.

Liquid Rubber must be thinned with solvent to achieve a sprayable viscosity. See recommendations below.

Equipment capable of spraying Liquid Rubber

Pump ModelMax.
Graco GH7333500 psi3.0 gpm 1/2 inch150 feet
Graco GH364036000 psi3.8 gpm 1/2 inch150 feet
GunShould be rated for spraying mastics. A 30-40 inch tip extension is recommended
Tip Size .017 to .021 with a 12 inch fan width

Note: Do not use a “whip” between hose and gun. This reduces flow and pressure which results in poor atomization.

Thinning Liquid Rubber

The “as shipped” viscosity of Liquid Rubber is 34-37,000 cp which is too high for spraying. By adding one gallon of Xylene Solvent to a 5 gallon pail the viscosity drops to 10,000 cp at 75° F. More solvent may have to be added at lower temperatures.

The spray atomization can be improved using a smaller tip size or adding more solvent to reduce viscosity.

Wash solvent from previous pump cleaning can be used for thinning after it is strained to remove dirt.


Caulking around fasteners is usually not necessary. The physical properties of the EPDM Liquid Rubber will produce a longer lasting seal around fasteners than caulks will because the latter will become brittle with age, causing loss of adhesion and cracking.

It is good practice to brush the rubber into the fasteners after spray application to ensure complete coverage. This procedure will be less time consuming than caulking.

answered Apr 29, 2018 by admin