Question: I want to renovate an old metal babies cot using your Eco paint.I intend having it sand blasted and my question, do I need to use a primer or undercoat before using your enamel? R.R.

Answer:  We sell 3 enamels, the prices vary. All three enamels will give a resilient, cleanable finish.  All are quite simple to apply and can achieve a quality finish.

The manufacturers say:

Bio Enamel Lacquer (either the Waterbased or the Oilbased)

A metal primer is required. It will provide anti-corrosive protection for steel, aluminum, brass and copper. Generally less effective on zinc and galvanized surfaces which require more specialised primers. The metal should be cleaned of all grease, dirt, processing soil, salt residues, weld scale, rust and other residue which is likely to affect the performance of a protective coating. Apply 1-2 coats (as recommended by the supplier) of Metal Primer thinly and evenly. Lightly sand between coats when completely dry. Finish with 2 coats of Bio Enamel Lacquer.

Volvox ProAqua Enamel

Metals must be primed with a coat of rust prevention paint.

We dont have an 'eco' metal primer, you'll have to chose a conventional product there. It is difficult to find a low voc/low toxicity option, so some research is needed.  You don't need an undercoat between the metal primer and the paint.

Both the Volvox Proaqua Enamel and Bio Waterbased Enamel are waterbased, and dry quickly. They have no smell, and are hard-wearing and you can get a good finish.  Volvox Proaqua Enamel is a medium sheen, Bio Waterbased Enamel is available in either a Semi-Gloss or Matt.  The Bio waterbased enamel is better priced because it is made in Australia (buy local, that alone is a pretty strong eco-credential!)

Bio oil-based Enamel is made from plant oils, it has no alcohol or drying agents so is slow to dry. In good weather wait a full 24 hours between coats, in humid cold and wet weather leave it a little longer between coats. It has a stronger lemon peel oil smell than the water based options.  It may require the use of Bio Thinner.  It has the advantage of being able to be painted onto existing oil paints, comes in matt, semi-gloss and gloss and some people feel it is a little more resilient than the water-based.  Note that the paint contains linseed oil, so the white paint may yellow a little over time.

Sorry to rant, I just realised you only asked about the undercoat!