Sandable primer is just impossible to find :(.

A note to 131S acrylic lacquer primer users:

This primer can be applied by spray gun or spray brush, piled on wet, directly to styrene, ABS, Acrylic, and Lexan plastic; cured epoxy, polyester, and polyurethane resin; the 'machinable' industrial tooling plastics ... without any fear of solvent damage to the substrate. Period.

In the twenty-five plus years I've been using 131S primer -- sometimes in near mud-pack thickness - I've observed no ill effects to the substrate.

I've read too many ill-informed posters over the years suggesting that this primer attacks the above materials; the horrible effects 131S has if applied to unprotected plastic surfaces. Those posters are wrong: the miss-informed spouting authoritatively miss-information to the unknowing. I'm tired of it.

131S is the holly grail of primers: It can be cut to water-thin consistency to preserve surface detail. Or it can be shot mud-thick to contour surfaces. Great flexibility of use, quick flash and dry time, tenacious adhesive property, and the primer won't chemically attack most substrates. If you can't find it, find it! You'll never go back.

(Oh ... those of you singing the praises of Mr. Surfacer as a primer substitute: What do you think Mr. Surfacer is, anyway? That's right: a 131S equivalent, repackaged at exorbitant markup for the not-too-bright hobby store and on-line shoppers).

Find, buy and use 131S primer. Let this be the last word on that.

David D Merriman lll

Hmmm...I just want to add a bit here. I hope I'm not being too sensitive and I know that Mr. Merriman's last message was specifically about 131S. But in the off chance that any of those comments were triggered by my post, I do want to make a couple of clarifications.

For several years in the 1980's I ran the paint shop at Standard Aero Limited which is the one of the worlds largest independent overhaulers of gas turbine engines (about 1200 employees here at the Winnipeg plant...branches worldwide). I wasn't "just" a painter...it was MY shop. I held two sets of government qualification stamps for the job: one from Transport Canada and one from the Department of National Defense. I probably inhaled more paint than most modelers will spray in ten lifetimes . People came to my shop from Portugal, Greece, Singapore...even from Cooper Airmotive in Texas to learn how to paint specialty material.

When President Reagan sent those F-111's to bomb Libya, I'm proud to say that the nozzle actuating cylinders on the TF-30 engines were painted by me personally. And they were painted by me because another aerospace company which had the afterburner contract for TF-30's didn't have anybody qualified to paint Sermetel.

Following my stint there, I went to a start up company called Advanced Composite Structures. My job there consisted entirely of finishing composite materials made by the Boeing factory. The composites came to us from Boeing (fairings, doors, etc) and my job was to spray them with an electroconductive coating, prime them and supervise the other painters in the correct process of doing so. The days were 12 hours long and I spent almost ALL of those days in full body chemical suit spray painting.

In my "spare" time, I've sprayed more than a few gallons of 131S at home...including on my '59 Corvette (which I COMPLETELY stripped down to bare fibreglass, inside and out...a full frame-off job).

Again, I only felt compelled to mention that in off-chance that my own post may have raised questions about my qualifications to comment on primers. Apologies if I'm being too defensive.

As I said, most automotive spray can primers (with the excpetion of the scratch-fillers which have a higher percentage of solids) can craze plastic. My comments were specifically about that. It's a subject about which I'm eminently well qualified to speak about.