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A few newbie type questions

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Old 01-08-2008, 10:18 PM
  #51  
JKEpps
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Default RE: A few newbie type questions

ORIGINAL: jantrit

Looks very nice,just a quick question, what purpose does the pva serve and is this applied before or after wax?
Well, I'll give you my understanding of it. Those with more experience can correct me. The wax serves to provide a very slick surface so that the resin doesn't stick to it. It takes quite a few coats of wax in most cases. I think 6 - 10 is the most common number of coats. In some cases, the wax used isn't enough to ensure that you get a clean release without damaging the plug. The PVA serves as an additional barrier to aid in clean releases. It dries to form a film that peels away from the plug and mold and layups. Some folks don't like to use the PVA because it leaves a residue on the plug and mold and layups that requires cleanup, and may even permanently stain the pieces. The PVA goes on after the waxing has been completed.

Hope that helps.

-Jorden
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Old 01-08-2008, 10:23 PM
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Default RE: A few newbie type questions

Hey, look what I found at my local Harbor Freight store. It's regularly $14, but on sale this week for $7. Looks like it'll be great for spraying on PVA. At $7, hey, it's worth a shot. I'll let you know how it goes.

-Jorden

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Old 01-09-2008, 02:12 AM
  #53  
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Default RE: A few newbie type questions


ORIGINAL: JKEpps

...I'll let you know how it goes.

-Jorden

Please do; I'm tooling up for an all-composite construction too. thanks for sharing your experiences!
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Old 01-09-2008, 10:10 AM
  #54  
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Default RE: A few newbie type questions

ORIGINAL: jantrit

Looks very nice,just a quick question, what purpose does the pva serve and is this applied before or after wax?


The PVA (poly-vinyl-alcohol) is a product that dries quickly and leaves a thin water-soluble film. It is applied after the wax and it makes the release of parts from a mold very easy and further reduces the chances of a part sticking resulting in damaged parts or a damaged mold. However, the PVA is difficult to use and obtain a glossy finish. If spraying, it is tricky to get it to set without tiny bubbles (you have to adjust the amount of water in it to the ambient humidity for proper drying time) and it is very sensitive to dust or other contaminates - spraying a glossy layer is more of an artform than doing so with paint. If brushing, it will leave some (very minor) brush marks on the part or the mold.

I've never had any trouble with staining the part using either epoxy or polyester resins. When using with epoxy, you need to understand that the epoxy will bond to the PVA (since it is water based and water is soluable). The result is that you will not be able to "peel" the PVA off but just rub it down with some water and the film will go away.
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Old 01-09-2008, 10:40 AM
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Default RE: A few newbie type questions

My experience with PVA is the same as TeamSeacats.

I never use PVA on a plug prior to laying up the mold. The streaky or little bubble finish with PVA is what the mold inside finish will be. I make sure the plug has many coats of wax applied over a couple of weeks to allow the wax to harden.

I will use PVA for the first couple of parts to come out of the mold. I can always fix those.

Ed S
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Old 01-09-2008, 02:42 PM
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Default RE: A few newbie type questions

ok thanks a lot, im 16 and just getting into composites, hoping to make some simple servo covers for my first little project. Looks like for all the work you put in you get a nice reward .
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Old 01-09-2008, 03:10 PM
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daven
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Default RE: A few newbie type questions

PVA can be tricky, but once you know what works for you and your gun its pretty easy to apply and you can get a mirror finish using it. I won't risk my molds to just wax, and always use PVA after waxing and prior to paint.

The biggest trick in applying PVA with a gun, is patience. I apply an absolute mist coat that barely covers the surface and let dry till smooth (about 10-15 minutes) before applying my 2nd coat. When a mold is new, I'll go to three coats until it gets to what I would call "seasoned".

I've had one wing stick in the molds, and won't go through that hastle of cleaning and repairing, and repolishing my mold back to a state I can pull good parts. So now I use PVA.

One of the things about PVA I never liked was removing it from the molds (the flanges) after the part came out. I've found a pretty good solution, I just take some 2" box sealing tape and stick it to the mold, rub it down, and pull it off. Removes the PVA residue / paint overspray very well.
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Old 01-09-2008, 06:12 PM
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Default RE: A few newbie type questions

Cheers Ed for the advice with the parting board,i had actually looked at the post you refered me to although for some reason the penny failed to drop,it has now,i can catch up with the rest of this very productive thread again,head is going wild now cant sleep thinking of moldings
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Old 01-10-2008, 06:44 PM
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Default RE: A few newbie type questions

JKEpps i am impatient also,cant wait to see the finished goods.
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Old 01-11-2008, 06:47 AM
  #60  
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Default RE: A few newbie type questions


ORIGINAL: bigben2k


ORIGINAL: JKEpps

...I'll let you know how it goes.

-Jorden

Please do; I'm tooling up for an all-composite construction too. thanks for sharing your experiences!
Well, I finally tried the sprayer last night by using it to spray PVA on the other half of my plug/mold combo. I used 20 PSI of pressure, and it sprayed on a nice mist of PVA. The spray pattern leaves a lot to be desired. This set definitely is not to be used for any kind of detail painting, except maybe with using a lot of masking, and that's a big maybe. In any case, it's definitely worth the $7 I payed for it. Plus it comes with the adapter needed to convert from the standard compressor size hose (3/8th I think) to 1/4 inch. I missed that little detail when I bought it, and ended up buying an adapter that I didn't need.

Hope that helps.
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Old 01-13-2008, 10:09 PM
  #61  
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Default RE: A few newbie type questions

OK, I've finally laid up the other side of the mold, and let it cure for nearly 24 hours. I seperated the halves, after a little coaxing, and voila! The first half looks beautiful, with a mirror finish to it. After a few anxious moments trying to get the plug to release from other half, it finally popped out. The other half was just as beautiful as the first. I am soooo pleased with the results. I'm totally hooked on mold making now. Even the details of the nickles I used came out great, even though the photos don't do it justice. The PVA did leave a pinkish hue to my plug. I wonder if it'll come out, or if it is permanently stained. I'll try and clean it up and see what happens.
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Old 01-14-2008, 11:53 AM
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Default RE: A few newbie type questions

Wow looks really good, this is inspiring stuff. It just clicked for me why you use the nickles, never would have thought of that until it would be too late .
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Old 01-14-2008, 02:12 PM
  #63  
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Man those picture came out HUGE!!!! That sometimes happens to me when I post pictures, and I don't know why. Am I doing something wrong ( iused a different application to "resize" the pics this time) or is it a RCU anomaly?
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Old 01-15-2008, 11:03 AM
  #64  
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Default RE: A few newbie type questions

rinse the molds with water and rub with your hand - the PVA will wash away. It's there because the epoxy started to dissolve and bond with it since water is soluble in epoxy. Fear not though, the PVA is still cleanly on the outside of the mold, just needs to be dissolved away.
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Old 01-15-2008, 08:54 PM
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Default RE: A few newbie type questions

JKepps, That happened to me on another post. I've been posting photos for years and that was the first time that it happened to me. I think it might be something to do with this board, just a glitch or a fluke. Normally it doesn't happen.

Several years ago, I worked for a company that did polyurethane molding for electrical connectors. We ran out of PVA mold release and when I called the company to order a rush shipment, he told me on the side that I could get by using something like PAM, that we use to keep our cookware from sticking. Hey, it worked!! Granted, it wasn't epoxy. And, we were pouring the poly into the mold, not brushing it on (which could disturb the finish of the PAM if used for one of our molds). Has anyone used something like this? And, if so, what were the results?

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Old 01-15-2008, 09:14 PM
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Default RE: A few newbie type questions

Bob,

I heard of using PAM cooking spray, Extra hold hair spray, and Teflon based sprays. I'm new to this, so I have not used any of those though.

-Jorden
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Old 01-17-2008, 05:47 PM
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Default RE: A few newbie type questions

Hey JKE have you put that stella mould to good use yet,full of anticipation to see a product here considering all the tidy work to date,awsome thread!
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Old 01-18-2008, 11:21 PM
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Default RE: A few newbie type questions


ORIGINAL: RabC

Hey JKE have you put that stella mould to good use yet,full of anticipation to see a product here considering all the tidy work to date,awsome thread!
I'm actually waxing it as I type this. I didn't have a chance to get to it earlier. Hopefully by the end of the weekend I'll be ready to do the first layups. My plan is to try different types of layups. I want to try a regular layup with epoxy and fiberglass, a layup utilizing painting in the mold, and a layup utilizing polyester gel coat and polyester resin. Hey maybe even carbon fiber and vacuum bagging. Just trying to see what I can learn.

-Jorden
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Old 01-19-2008, 06:56 AM
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Default RE: A few newbie type questions

...and a layup utilizing polyester gel coat and polyester resin.
Warning. If your mold is made of epoxy or if previous layups were epoxy subsequent polyester layups in that mold may not cure completely.

Ed S
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Old 01-20-2008, 03:21 PM
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ORIGINAL: Ed Smith

...and a layup utilizing polyester gel coat and polyester resin.
Warning. If your mold is made of epoxy or if previous layups were epoxy subsequent polyester layups in that mold may not cure completely.

Ed S
Interesting, I wouldn't have thought so. I would have figured that it wouldn't matter, especially since there is wax and PVA seperating the two. Thanks for letting me know, as I had no idea. That's part of the reason I want to try different things to see what happens.

I'm moving on to my next project, making a mold of a fiberglass fuse I have. Man getting the wax out of the panel lines is a pain. I'll start a thread on that one later when I get a little farther along.

-Jorden
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Old 01-20-2008, 11:24 PM
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Default RE: A few newbie type questions

Well, just finished the waxing of the molds. 10 coats of carnauba wax with at least 45 minuites of drying time between coats. It'll let the wax "harden" for apx 24 hours or so before I try to do my first layups. Hopefully by Tuesday evening I'll be in progress!

-Jorden
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Old 01-21-2008, 04:15 PM
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interesting...any idea why? Is it moisture related?
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Old 01-21-2008, 08:03 PM
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Default RE: A few newbie type questions

just a quick question,
im making a mold for a .25 - .32 P47. im wanting to add panel lines and rivet detail to add scale effect. by the time you wax the plug, make the mold and then wax the mold, will any of that scale detail come in the finished product???
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Old 01-22-2008, 02:45 AM
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Default RE: A few newbie type questions

Hey Jake, glad to see another NACRA driver on here. [sm=bananahead.gif]
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Old 01-22-2008, 05:15 AM
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Default RE: A few newbie type questions

just a quick question,
im making a mold for a .25 - .32 P47. im wanting to add panel lines and rivet detail to add scale effect. by the time you wax the plug, make the mold and then wax the mold, will any of that scale detail come in the finished product???
Yes they will. Look at it this way. The slightest imperfection will show up in a mold. So panel lines and rivets will be no problem.

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