I’ve seen some often installers preparing a self-made primer by using their standard binder and adding whatever available solvent they had in the van.
All of them probably know that polyurethanes suppliers have a portfolio of speciality products for priming, tailored to main kind of sub-bases as concrete or asphalt and they also know their self-made solution, will not be technically better that those specially designed products.
However, sometimes the planner forgot to order the primer or they were short of on the job site, and a solution is needed. Better to use a self-made one that install the first surfacing layer without priming. Priming is essential for a successful surfacing job and reduce the risk of warranty claims.
To do the self-made primer these are my recommendations:
Thin your normal polyurethane binder by mixing it well with about 40 to 50% proportion of solvent as Ethylacetate, Butylacetate, toluene or xylene. Solvents containing alcohol or water must no be used.
Apply the primer with a roller or a brush, in case of small areas, or spray it, using low pressure airless equipment. Always apply a thin layer to avoid foaming effects and wait a minimum of 2-3 hours to allow solvent evaporation.
Start laying the first surfacing layer when the primer is sticky and always within 24 hours of priming. Prime in short areas that will be surfaced within this maximum time. In case of rain, you must repeat the priming as water will impair adhesion of the next coat and so eliminate its functionality.
And now a final and the most important recommendation: Consult the technical service of your supplier before starting your chemical researcher career, inventing a mix of unexpected effects. Some of them may be not funny at all.
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