Help! Red oil paint not opaque enough...
 

I am doing a painting right now and I paint pretty thin. But not thin enough to see through the paint, this problem only happens when I use my red colors. Does anybody else have this problem? Has anybody solved this problem. I do not want to paint really thick and I do not want to have to keep on painting layer upon layer. The colors I am useing are:
Alizarin
Cad. red med, light, and dark.
Perm rose
My medium is also
Varnish, Linseed oil, Turp, and a bit of Cobalt drier
I have been painitng for over 17 years in oil paints and I have not found a brand that is opaque enough.
I have used Van gogh, Rembrandt, and Winsor and Newton Professional kind.

Any suggestions would be great, or substitutions.

What about mixing in a tiny bit of Titanium white? I hear that's also a good idea for glazes of any kind (mixing in the tiniest bit of white) so they don't appear to float on the surface.

Most paints art not opaque painted thinly especially in one layer. Ditch the mediums, they are deleterious and just use a thinner to get the paint to the consistency you want.

Alizarin is one of the most transparent colors there are. Do not mix white to make any red opaque. It will only dull it. If you need to lighten a red up add some genuine Naples yellow.

A very opaque, albeit pricey red, that is the most opaque I have ever used is the Vermilion red by Michael Harding, It is $50 a tube and well worth it .It is sold by the Italian Art Store, www.italianartstore.com. He also makes a genuine Naples yellow. The light one is the one you want. All the other manufacturers make a mix of a cadmium and white. It is not the real thing.

Try painting the under-layer with an opaque earth red such as indian red or venetian red. You can then use your regular colors over it. You might even find you don't require the extra punch that cadmiums offer.

Alizarin and perm rose are very transparent pigments and so is your medium containing varnish. I don't know if there is a brand that can overcompensate for those choices. I use Michael Harding paints which I feel are far superior to any other brand I've tried.

You can add opacity to your cad reds by adding yellow ochre or gold ochre in the appropriate value. Interestingly, you can add up to 50% yellow ochre into cadmium red, and still have it read "cad red."

Unlike adding titanium white, adding yellow ochre will not change the value or temperature of the cad red. Marvin and Sharon are right, Aliz and Perm Rose are both transparent. Stick with at least the semi-opaque reds, like the cads.