Got clear, thinner and retarder enroute.  It starting to rain more and dry days will be fewer so I ordered some retarder.  Found some threads on portions to mix in.  What exactly does it do?  Im guessing by the name that it slows down the drying time.  Thanks folks!

When I use retarder, which is not often, I use Randolph's.  Makes sense because I use Randolph's dope.  The directions say to use *up to* 20 % of the total amount of thinner used.  That is way too much.  A lot of the time I'll thin the dope to 60% thinner.

To answer your question, yes it slows down the drying time.  If there is too much retarder the clear can be so slow it will so bad things to you colors, assuming you are using it for a top coat.  I try not to use it unless I get some blushing, even then an extra coat of thinned clear usually fixes things.  

I guess the answer is to go light on the retarder and increase as necessary.  I live in Seattle.  It's been know to rain a little here too.  Your Dad is right, just tread lightly!

Hi Sean,

It has been alluded to that too much will cause problems.  I have found that to be very true.  We had a new big stunter and was heading to KOI.  Had to paint in bad weather so kept adding retarder, which was STUPID! LOL!!  The bottom of the model was a dark turquoise, and at the very end of the fuselage the color disappeared!

I think Bill Byles will back me up here when I say that the retarder make the thinner act "hotter".  In the automotive lacquer business, the thinners are in "heat" ranges and the higher the heat rating, the longer drying the thinner is.  This allows the lacquer to create a chemical bond with the under layers better.  Of course if used at the wrong temp, it can cause problems.  Hope this helps.
Shooting with dope and getting blush can be aggravating! And if a little is good, a whole lot is NOT better!

BIG Bear
RNMM/AMM

As noted in the other posts here retarder makes the dope dry more slowly, which may be needed in very hot conditions or in high humidity.  However, sometimes the conditions are just outside of the envelope of even retarder to make it possible to get the results you are looking for.  Here in So Cal we can spray most anytime it isn't raining or over about 95* F (both rare conditions); I generally try to not to go with more than 10% of the total thinner as retarder.  You may be able to use a smidge more but don't keep chasing it if it doesn't seem to be helping - wait for better conditions (I know, I know...but I've got this gun full of dope and I just have to get it done today!)

It was good to see you out at Whittier Narrows a couple of months ago, Sean.

Bill Byles

Great hanging out with you too Bill!  Nothing gets the juices flowing better then watching other people fly their airplanes. It wont quite get there, but the finish on your Lark got me especially motivated!

I'm 2 coats in.  I stole the hydrometer out of my cigar humador (Xikar digital hydrometers are super accurate and easy to calibrate.  Going to get another one specifically for painting).  I'm not going anything over 55% humidity with 10% retarder.  It could probably handle more, but I would rather not try to find that limit.  There's no real rush (for once) to get it finished...though it is very tempting to just bolt the motor on and go fly it!

One question I do have.  I did some preliminary sanding on the bottom with 1000g.  Im getting traces of red on the sandpaper where I dont think I should anymore.  Again this is after 2 coats.  Is this normal (some of the red losening and mixing in with the clear somehow?)  or am I not laying the clear on enough?  Dont want to sand through any paint/ink lines/decals.  Thanks!

Great hanging out with you too Bill!  Nothing gets the juices flowing better then watching other people fly their airplanes. It wont quite get there, but the finish on your Lark got me especially motivated!

I'm 2 coats in.  I stole the hydrometer out of my cigar humador (Xikar digital hydrometers are super accurate and easy to calibrate.  Going to get another one specifically for painting).  I'm not going anything over 55% humidity with 10% retarder.  It could probably handle more, but I would rather not try to find that limit.  There's no real rush (for once) to get it finished...though it is very tempting to just bolt the motor on and go fly it!

One question I do have.  I did some preliminary sanding on the bottom with 1000g.  Im getting traces of red on the sandpaper where I dont think I should anymore.  Again this is after 2 coats.  Is this normal (some of the red losening and mixing in with the clear somehow?)  or am I not laying the clear on enough?  Dont want to sand through any paint/ink lines/decals.  Thanks!

Hi Sean,

One thing about using retarder in the butyrate...sometimes it will slow the drying down enough that the thinner/retarder/clear dope mixture will stay wet long enough to "float" the underlying color dope finish & cause it to appear faintly on the sandpaper.  I don't know if that is what is happening with your project but is something to be aware of.  This is most likely to happen when you apply clear butyrate dope over a lacquer color finish (as I found out a few years ago on a Nats ship I built.)  As most everyone discovers, getting to a good finish is part art & part shade tree science.

The other thing is, as you mentioned, you may need to get more clear on prior to sanding.  You can only apply just so much dope per coat, so I would put on probably 4 coats (two coats per day) prior to sanding.

Thanks for your comments on my Lark finish; I built that airplane in 1993 and the finish is all butyrate dope.  The colors are Randolph and the clear topcoats are Sig Lightcoat.  It doesn't have a lot of flights on it - about 455 over the 21 years it has been around but it's holding up pretty well.

I hope to see some photos of your airplane when it is finished!

Bill