Marks on gelcoat

[ondarvr]

As mentioned, 1% pigment is very low and may cause problems. And trying to build up 450 microns with a 1.7mm can also cause problems, especially if you're trying to use a brushing gel coat to do it.

Wax doesn't typically leave any surface discoloration if it's applied correctly, as in being buffed to a gloss. Even 100 coats won't cause a problem like that. Not buffing it off correctly can, and then you get a uneven rough surface on the mold that can be sanded off. This time you also mention the mold surface showing an odd surface too, so this is on the mold surface and being transferred to the part?

1mm of tooling gel is rather thick, and thick gel coat can trap air, plus VE tends to foam up a little. If it's applied thick, any air created by it foaming can't escape easily, so you can get a poor surface form the porosity that is transferred to the part, but is only the surface.

You have several things that could create a problem like this.

Is there a rough or odd surface on the mold in these spots, and are they in the same place every time?

Trying to get any gel coat, let alone brushing gel coat, to a thickness of 450 microns is not easy with a 1.7 mm tip. Why are you using such a small tip?

1% pigment is ultra low unless it's some super high concentrated pigment. Why are you using that low level?

Are you following the directions on the can for that exact mold release wax?

What catalyst and a what percentage are you using in both the gel coat for the mold and the part?

 

[Jonathan Muller]

hello! So far this is what I have used on all the pieces I have laminated 1% concentrated pigment for gelcoats and for ploisteric resins. In my case, the gel coat will be painted in an automotive system with acrylic paint and acrylic varnish. I put the pigment so that it is the same color as the part. The gun nozzle is 1.8 and so far all the parts I have made, 14 parts and have come out perfectly well. I used a special gelcoat for the gun. This is the gelcoat on the pieces. The mold gelcoat was applied with a brush. I applied wax according to the technical data provided by the manufacturer. Applied, left to haze for 5-10 minutes, then polished. I applied 6 layers because the molds were newly made and the day before applying the spray gelcoat of the part in the mold I applied another layer. The same stains on the mold are also transferred to the piece. Regarding the thickness of the gelcoat of 1mm, that's what I found in the manufacturer's technical sheet and indeed many pores remain even visible. Those spots are not felt with the fingers or are not a rough surface. They are just a visible aspect. They are not in the same place. In different places than other times. I use slow MEKP catalyst. For the mold gelcoat I used 3% according to the technical data and for the part gelcoat 2% the same according to the technical data

 

[ondarvr]

Wax won't cause those marks if polished.

1% pigment is fine for that purpose, but spray technique and the tip size can create problems. The way gel coat comes out of a small tip makes it difficult to build it up thick enough without blowing it around on the surface, this movement can change how the pigment stays blended in the gel coat. Some of those spots looks like its sagging or moving on the surface.

When you say special gel coat, what does that mean, is it formulated for spraying, is that the special part of it?

If these spots keep moving around and aren't located in just one place on the mold, then it has something to do with how you are applying the gel coat, or the gel coat itself.

Building 14 that turned out good means you are doing something different now, or this batch of gel coat itself is different.

 

[Jonathan Muller]

Wax won't cause those marks if polished.

1% pigment is fine for that purpose, but spray technique and the tip size can create problems. The way gel coat comes out of a small tip makes it difficult to build it up thick enough without blowing it around on the surface, this movement can change how the pigment stays blended in the gel coat. Some of those spots looks like its sagging or moving on the surface.

When you say special gel coat, what does that mean, is it formulated for spraying, is that the special part of it?

If these spots keep moving around and aren't located in just one place on the mold, then it has something to do with how you are applying the gel coat, or the gel coat itself.

Building 14 that turned out good means you are doing something different now, or this batch of gel coat itself is different.

hello! thanks for the reply! I will use a larger nozzle like 2.5mm or 3mm and I will follow up if those spots appear again. I have another question related to lamination. I would like to change the lamination process from manual lay up to vacuum infusion with polyester resin and fiberglass. What type of fiberglass should I use to facilitate the best impregnation of the fibers and to obtain the best possible impact and shear resistance. I would like the thickness of the final laminate after infusion to be around 6mm. thanks.

 

[ondarvr]

These guys have training videos. And the products they sell are available in Europe.

Materials, equipment and training for advanced composites with next-day shipping and expert technical advice. - Easy Composites https://www.easycomposites.co.uk/

 

[Jonathan Muller]

These guys have training videos. And the products they sell are available in Europe.

Materials, equipment and training for advanced composites with next-day shipping and expert technical advice. - Easy Composites https://www.easycomposites.co.uk/

I've been following them for a very long time. But unfortunately they only have videos with carbon or kevlar infusion. I haven't found many videos with fiberglass.

 

[ondarvr]

I've been following them for a very long time. But unfortunately they only have videos with carbon or kevlar infusion. I haven't found many videos with fiberglass.

Glass is similar, all the same rules apply.

It comes down to the part shape, part size, and exact fabric type and weight used to dial in the process. So you are just looking for generic methods, because even if they use glass in the video it wouldn't mean you would do the exact same thing.