Don't know the answer to your first question.

I brush the first coats of clear, too lazy to hook up spray and clean it afterwards.

I use butyrate dope all te way thru now after a little fiasco of getting nitrate and butyrate mixed up.  If you try spraying the thinned  dope for the first coats to seal the material used you will learn real fast why we brush the first coats to seal the material.  I tried it many, many years ago when I got my first spray kit.  Did not take long to realize I was blowing the dope right on thru the material.   

Guys,
I was wondering what is added to dope to make it non-tauting? I heard that GMA use to add castor oil but this seems like it would reduce the grip of the paint to the surface.

Second question - after we get the covering adhered to the frame why do we brush the first few coats on instead of spraying?

Best,      DennisT

Hi Dennis,

When finishing models I use dope thinned as required out of the can.  The reason for brushing on the first three or so coats is that the brush will act as a squeegee pushing the dope through the silkspan or silk to fully encapsulate the covering material (on both open-bay areas & on balsa), providing maximum grip of the dope to the substrate.

For the first three coats on the open bay areas only I use tautening dope thinned as required with no plasticizer added, brushing it on to tauten the covering.  When about 3 coats of tautening & non-tautening dope have been brushed on (non-tautening for the solid areas & tautening for the open bay areas), for all further dope through color I start adding a small amount (about 1/4 to 1/3 of the recommended) of Dave Brown's "Flex-All" plasticizer to prevent pulling of dope in the fillet areas for all of the dope finish through all of the color.  For all of the final clear dope finish on top of the color I add the full amount of plasticizer recommended (& no more) to non-tautening dope to further prevent dope pulling up in the fillet areas.  I highly recommend using Dave Brown's "Flex-All" plasticizer because it is a known quantity; when you start experimenting with castor oil, etc. you become an experimental chemist on your labor of love (whether it be a classic or current stunt weapon) & risk having problems that are easily avoidable.

And Dennis - you are correct in that plasticizer does reduce the inter-coat adhesion of the dope coats, so it is important to not overdo the plasticizer.  There is a fairly fine balance between enough plasticizer to prevent pulling the dope in the fillet areas & too much plasticizer which will result in loss of inter-coat adhesion.