Author Topic: Talc and Dope mixing (Read 2693 times)

wwwarbird · « **on:** April 04, 2011, 08:40:06 PM »

I've never tried mixing talc or zinc sterate into my dope during finishing before. I'm thinking of trying it out on the final couple of prep coats on the Combat Streak that I'm currently finishing up to see how I like it.

If you use talc, (baby powder?) what product is favored? How much of either do you typically mix into a pint of thinned clear?

wwwarbird · « **Reply #1 on:** April 04, 2011, 09:31:57 PM »

Thanks Ty. Hmm, I've never heard of using corn starch. Why do you like that or sterate more than talc?

Dave Holtsclaw · « **Reply #2 on:** April 04, 2011, 10:01:19 PM »

where do you get zink sterate?

dennis lipsett · « **Reply #3 on:** April 04, 2011, 10:32:22 PM »

Give Randy a call at Aero Products. if it's good he's got it.

wwwarbird · « **Reply #4 on:** April 04, 2011, 10:43:34 PM »

I do believe Randy carries zinc sterate, but if I remember correctly the stuff is a little spendy.

PJ Rowland · « **Reply #5 on:** April 04, 2011, 11:53:16 PM »

I would debate the weight difference between talc and ZS..

depends on what sort of formula you use - I personally like to have it running more than " Claggy " when its runny thinned you get a nice coverage. Let it dry a single day then go at it.

ive even sanded back after 6 hrs wait time. depends on temp.. it does get hot in Australia

Will Hinton · « **Reply #6 on:** April 05, 2011, 07:54:47 AM »

I buy my ZS at the local sporting goods store - weight lifters use it for grip. I get it in blocks that are easily scrubbed down to powder. I think it mixes easier than talc, and I also think it is definitely lighter. (Anyone do a weight comparison?)

Don Hutchinson AMA5402 · « **Reply #7 on:** April 05, 2011, 08:29:54 AM »

You can get zinc stearate from Sciencelab.com. It is a bit pricey, $58.00 for 500 grams but that will do a whole lot of airplanes. It is a jar about 4 inches dia by 6 inches high.
Don

Randy Powell · « **Reply #8 on:** April 05, 2011, 09:37:01 AM »

I have used both zinc sterate and talc (I used to by talc from Tap Plastics but they stopped carrying it). I mix it about how Ty describes the thin it down enough that it will go through my cheap Harbor Freight gun. Usually about 4oz of unthinned non-taunting dope an a heaping tablespoon of talc (or ZS) then thin maybe 80% to get it to go through the gun. Two coats of filler (more or less) then inspect. May re-shoot on low areas.

Geoff Goodworth · « **Reply #9 on:** April 05, 2011, 06:46:59 PM »

Here's a crazy one.

I have actually gone to my garage at night and caught cockroaches eating the cornstarch filler on one model that I used it on.

I repaired the damage last year and applied a couple of light coats of Duplicolor to the airframe before I went to Europe for a couple of months last northern summer. When I arrived home, I found the model had been chewed again. The repair this time has involved cutting back the LE of the stab and replacing the chewed bits with 1/8" dia dowel. Between the first chewed LE, the sanding out and second chewing, 1/8" had been removed from the LE. The second time, the square TE of the stab was chewed as well and I still haven't figured out how to fill it.

Next time, I'm going to try borax in dope to get even with the roaches.

RandySmith · « **Reply #10 on:** April 05, 2011, 08:13:34 PM »

Quote from: PJ Rowland on April 04, 2011, 11:53:16 PM

I would debate the weight difference between talc and ZS..

depends on what sort of formula you use - I personally like to have it running more than " Claggy " when its runny thinned you get a nice coverage. Let it dry a single day then go at it.

ive even sanded back after 6 hrs wait time. depends on temp.. it does get hot in Australia

Hi PJ

You can debate it but you would be wrong, ZS is lighter than talc or corn starch, It also does not absorb the dope and sands better than both, It also doesn't settle to the bottom of the jar light either do untill a long long time.
Talc will sit in the bottom of the dope jar pretty quick because it is heavier than the dope. I have used most everthing you can imagine and ZS is the best, That is the only reason I even mess with carrying the stuff, You also need the ultra fine and refined Lab grade...NOT the grind they use as a white paint pigment..That ZS is more like sand than shifted flour

Regards
Randy

wwwarbird · « **Reply #11 on:** April 05, 2011, 09:12:15 PM »

Randy,

I've looked off and on before and I've never found Zinc Sterate on your website. What's the scoop?

RandySmith · « **Reply #12 on:** April 05, 2011, 10:40:43 PM »

Quote from: wwwarbird on April 05, 2011, 09:12:15 PM

Randy,

I've looked off and on before and I've never found Zinc Sterate on your website. What's the scoop?

Hi Wayne

It is in my catolog.
I have 1000s of products, all of them are not on the site, and there is not enough profit in them to hire someone to add all the items, As much as I would like to have everything there I cannot afford to do this. However it is in , and has been in my catalog for decades. I sell it by the pint or quart

Regards
Randy

john e. holliday · « **Reply #13 on:** April 07, 2011, 08:43:40 AM »

And the price of the ZS? I tried cornstarch and was thoroughly disappointed. So the last finish I did was Talc and Dope. Waiting several days after two coats brushed on to sand.

Bill Little · « **Reply #14 on:** April 07, 2011, 05:49:04 PM »

A point about the ZS, it takes less to make the filler than we usually use in making the dope/talc mix, so it comes out even lighter.

I remember, "back in the day", reading every construction article and it would say "mix equal amounts of dope, talc, and thinner. It doesn't take NEAR that much of the ZS that Randy carries.

RandySmith · « **Reply #15 on:** April 08, 2011, 01:30:16 PM »

Quote from: john e. holliday on April 07, 2011, 08:43:40 AM

And the price of the ZS? I tried cornstarch and was thoroughly disappointed. So the last finish I did was Talc and Dope. Waiting several days after two coats brushed on to sand.

The special ZS filler I have made is 19.95 a pint and 29.95 per qt, A qt will last the average modeler years, It goes a long way
It is also a very extreme fine grind, and sand better than anything I have used

Regards
Randy

PJ Rowland · « **Reply #16 on:** April 09, 2011, 10:58:26 AM »

" You can debate it but you would be wrong, ZS is lighter than talc or corn starch "

I guess what I actually meant by that was :

Ive had trouble sourcing the quality ZS you carry, so I don't use ( but would like to ) - I was thinking more along the lines of the AMOUNT of talc I would use to complete a model. Considering how much powders off to start with, and how thin you apply it.

I have no doubt in my mind at all - that ZS is better ( And i will conceed due to being uninformed ) Lighter - Hence you carry it - and it would be premium quality. It would make an interesting exersise to be able to know to some level of certainty what the weight difference is after sanding is complete.

4 g ? 6 g ?

wwwarbird · « **Reply #17 on:** April 09, 2011, 08:38:36 PM »

A little too much information?

wwwarbird · « **Reply #18 on:** April 11, 2011, 11:15:11 PM »

I ordered a quart of zinc sterate from Randy today. It'll be interesting to give it a try.

I plan to brush it on if it's going to sand as easily as I'm expecting it to. So, a good starting point is about one heaping tablespoon to 4oz of thinned dope?

Neville Legg · « **Reply #19 on:** April 12, 2011, 02:43:49 AM »

I assume you are using Non-Shrinking Dope?

Cheers

wwwarbird · « **Reply #20 on:** April 12, 2011, 08:12:26 AM »

Nope, was planning on using it with Brodak clear mixed about 50/50. This would be on polyspan after an initial 2 or 3 coats of straight 50/50 clear without sterate.

Neville Legg · « **Reply #21 on:** April 12, 2011, 12:18:58 PM »

Commercial sanding sealer doesn't shrink, well the stuff I buy in England doesn't anyhow!. You can brush it over fairings and fillets without the worry of them lifting. So that's why I would use non-shrinking dope.

Cheers

Bill Little · « **Reply #22 on:** April 15, 2011, 01:25:15 PM »

Quote from: wwwarbird on April 12, 2011, 08:12:26 AM

Nope, was planning on using it with Brodak clear mixed about 50/50. This would be on polyspan after an initial 2 or 3 coats of straight 50/50 clear without sterate.

Hi Wayne,

Do you have any plasticizer/flex additive? It would definitely help with the "non-tautening" qualities which would allow it to go over fillets, etc., with out as much worry.

Actually, I don't use tautening dope anymore except for a couple coats on open bays. Not sure just how strong the Brodak's is in the "tautening" arena compared to Sig Super Coat Clear though.

Big Bear