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Building Tips and technical articles. => Paint and finishing => Topic started by: Russell Shaffer on April 15, 2009, 08:23:24 PM
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I'm sure this has been covered, but what mix should I use for talc and dope as a sanding sealer and filler? Thanks for any help.
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This presumes you are brushing; if spraying, make suitable adjustments.
Add enough thinner to the clear so it will flow out smoothly. Then add about a rounded Tablespoon of talc per quart of the mix and stir. Let it settle for about 10 minutes, and then brush. You must wear a dust filter when sanding; talc can do horrible things to your lungs. (And have you priced a replacement set recently?)
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Thanks, Ralph. I'm brushing and I appreciate the tip about the mask.
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I usually use more talc than that. The most I can keep suspended.
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So Randy, it's kind of like baking soda on a battery? If there is too much to keep suspended and there is a layer on the bottom of the jar, just don't dip the brush into the bottom? Makes sense, I am going to sand it off anyway and that should smooth it out.
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Wet sand & you will not need a mask.
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The filler I am using right now is the best I have ever had. It has Talc and Micro ballons in the clear, and man does it fill well. 2 to 3 coats on bare wood and you are ready for promer. I sand with 320 first before I apply the primer... I really like the results. I didn't know about the mask though, thanks for the tip.
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Well, talc is a mineral, a rock that has been pulverized! But if it is safe to dust onto a baby's bottom, why is it harmful?
We inhale all sorts of micro-particles: dust, pollen, etc. And we typically live a long time (at least I have--- so far!)
Floyd
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Some talcs were found to contain asbestiform materials. Asbestifrom, as in longish fiber shapes.
Chemically, some talc is close to some forms of asbestos.
AFAIK, no modern (last 15 - 20 years) talc has asbestiform components.
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I've used talc, as Randy says, so much it settles to the bottom. Problem is, doesn't seem to fill the grain very well. Actually, not much different from just plain dope. Maybe I'll try microballoons next.
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Marchiori E, Lourenço S, Gasparetto TD, Zanetti G, Mano CM, Nobre LF. Pulmonary talcosis: imaging findings. Lung. 2010 Apr;188(2):165-71. doi: 10.1007/s00408-010-9230-y. Epub 2010 Feb 13. PMID: 20155272.
Here’s a reference on talc! In short, it really can bugger up your lungs.
The argument that we inhale all sorts of other stuff so what harm does it do , was used by the smoking lobby for years.
We do put it on babies bottoms but that is not inhaled , although it may reach their peritoneal cavity where it is is linked to ovarian cancer etc in women. Better to use corn starch powder ( I’ve actually tried it in dope, seems to work ok) .
Happily in these days of Covid 19 we all know about masks! I’d be wearing an n95 for all vigorous sanding, unless outside with a tailwind!
Cheers Dr Phil ( very novice stunter, but better than novice doctor!)
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i just bought this from walmart
https://www.walmart.com/ip/Talc-Powder-Laboratory-Grade-500-G/196773579?irgwc=1&sourceid=imp_U-TUtCy5sxyNUOjTvSxDjz0rUkA2hGXl3URfU80&veh=aff&wmlspartner=imp_150372&clickid
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Russell,
You might want to consider using corn starch or better yet, Randy Smith's zinc steroid. The ZS will be a third to half the weight of the tale, I would still use a mask when sanding it off or sand outside.
Best, DennisT
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Russell,
You might want to consider using corn starch or better yet, Randy Smith's zinc steroid. The ZS will be a third to half the weight of the tale, I would still use a mask when sanding it off or sand outside.
Best, DennisT
Zinc Stearate. That, or Randy has been juicing.
Brett
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I have used Talc all of my life and not liked it because of the sticky dust everywhere. Is Zinc Stearate any better or just safer. Anybody mixed it with Mod Podge by any chance?
Ken
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I have used Talc all of my life and not liked it because of the sticky dust everywhere. Is Zinc Stearate any better or just safer. Anybody mixed it with Mod Podge by any chance?
Ken
I use Zinc Stearate and it’s amazing stuff! Powders off, not sticky, mixes well with dope and good adhesion for painting and masking. Never used mod podge so I can’t comment or speculate on that
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Mod-pod used for ahering doc paper or silk-span also poly-ester materials. It does make the balsa surface harder when sanded. It is not a filler.D>K
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Ops, my bad (Zinc Stearate), spell check doesn't catch it if you have the right thought, but spell the wrong word correct. Only thing with tale (besides some having the asbestos) is it absorbs lots dope, the ZS seems to absorb less so you save some weight.
Best, DennisT
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Doc,
Didn't you once advise (or some else) you can add talc or zinc stearate to water based non-odor Polycrylic or Verathane for filling bare balsa or over doctors paper on solid surfaces? Both harden nicely and sand (powder) off, filling the grain.
Masks & respirators are essential with any kind of dust. Lung damage is irreversible and not to be taken lightly.
Steve
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You expect the old DOC to own up to that? I quit using talc and dope when I was told about spray primers. D>K
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So Randy, it's kind of like baking soda on a battery? If there is too much to keep suspended and there is a layer on the bottom of the jar, just don't dip the brush into the bottom? Makes sense, I am going to sand it off anyway and that should smooth it out.
No matter what powder you put into your clear dope, it'll settle out. So get it mixed to your satisfaction but just like colored dope, plan on stirring it up if it's sat for a day or more.
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have you tried silkspan or carbon veil to cover bare wood instead of talc&dope?
the benefits are multiple: lightweight, stiffen the airframe,prevent wood cracking, makes a harder surface against dents and requires almost no filler and much less primer resulting in a lighter and stronger airframe. extra bonus> no mess sanding powder.
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Fred,
I use the medium silkspan over all the wood surfaces then fill with 4 coats of clear followed by 1 coat of ZS+clear. Sand smooth then 1 coat of clear to seal the ZS and go to block color coat. I have not had good results with just filling the straight wood surfaces as at some point it shows through. The CF will also work and may take less dope to fill but it is a little more trouble to go around edges and curves. Also used light weight silk, very strong but takes lots of dope to fill. 3/4 oz fiberglass cloth also works, very strong, can use dope and is about the same as silkspan. Bottom line is for full fuse silkspan is a good option, on a profile I have used the 3/4 oz fiberglass cloth and dope adds a little stiffness (you want the 3/4 oz fiberglass not the 1/2oz, the difference is the thread count is~1/3 less in the !/2 oz and you need to fill with more dope).
Best, DennisT
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Several have recommended CF Cloth for stiffening flaps. What thickness? What about weight?
Ken
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Fred,
I use the medium silkspan over all the wood surfaces then fill with 4 coats of clear followed by 1 coat of ZS+clear. Sand smooth then 1 coat of clear to seal the ZS and go to block color coat. I have not had good results with just filling the straight wood surfaces as at some point it shows through. The CF will also work and may take less dope to fill but it is a little more trouble to go around edges and curves. Also used light weight silk, very strong but takes lots of dope to fill. 3/4 oz fiberglass cloth also works, very strong, can use dope and is about the same as silkspan. Bottom line is for full fuse silkspan is a good option, on a profile I have used the 3/4 oz fiberglass cloth and dope adds a little stiffness (you want the 3/4 oz fiberglass not the 1/2oz, the difference is the thread count is~1/3 less in the !/2 oz and you need to fill with more dope).
Best, DennisT
i just use 2 part primer over the doped silkspan,or doped carbon veil it fills everything and still manage to be light. no other filler added. maybe the primer is the key here.
the white is a very thin coat of spectra prime by sherwin williams. not sure if available abroad
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I think the best choice is 20g/m2 Carboweave +/-45, vacuumed to the 1/32"...1/16" balsa flap skins. But if you want to do it well, with a symmetric behaviour, you need both +/-45 and -/+45 sheets. Total laminate weight will be about 40g/m2 (1,18oz./sq. yd.).
Another good option would be a light Rohacell (31) core and a little thicker Extreme cloth, 60g/m2 or so. L
Can you recommend a source for these? Best I could find was $135 a yard and it was out of stock.
Thanks - Ken
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I ordered directly from CN-Models, received a few weeks ago. But now when I checked, their website is not working but theycan be found in facebook.
Textreme should be easier, though. Check R&G or some US equivalent. L
Thanks Lauri - I researched all of the above and couldn't find anything reasonable under 100gsm. I did find some Textreme but it was $138 m2 plus shipping from Mars. I got "acceptable" results using silkspan and MonoKote. If by some divine intervention I get my balance back and get off this 530 plateau I am camped out on I will spring for $200 flaps. Each birthday I keep hoping my age will go down but it never does. :'(
Again, thanks for the leads - Ken
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I have never seen a need to mess with talc, cornstarch, etc. I cover bare wood with medium silkspan and fill that silkspan with clear dope. It takes a while, maybe five coats, perhaps more, but it works out OK for me. I might need a bit of the Brodak White Primer to fill in some areas.
The silkspan adds some stiffness to flat components like flaps. CF cloth would no doubt provide more stiffness but the silkspan is easy to work with and I would rather stay with that.
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The filler I am using right now is the best I have ever had. It has Talc and Micro ballons in the clear, and man does it fill well. 2 to 3 coats on bare wood and you are ready for promer. I sand with 320 first before I apply the primer... I really like the results. I didn't know about the mask though, thanks for the tip.
I would be more concerned about my health with micro balloons which are made from crushed glass powder than i would worry about talc. Crushed glass is also used in some industrial sanding sealers too. Its a good way do dispose of broken glass and profit from the consumer all at the same time. Just put some warning label on it. 😁👍