Three strikes with PR - ugh!

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alankulwicki7

alankulwicki7

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Vadnais Heights, MN
Hey all,

Trying to cast a decal on tube for the first time and here are the problems:
1. Decal pulled away from tube
2. Paint on tube crinkled
3. Resin shrunk so the end of the tubes stick out of the resin.

I've done some casting with PR before with decent success. This is the first time using resin saver type molds and I am pretty disappointed to say the least.
The decal tubes are easy to redo but the top tubes in the photo take a fair amount of time to make. Plus the material is in limited supply :eek:

Any advice?
 

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Are you sealing the decals before casting?
I put 2 coats of thin ca, let cure for a day then cast

As far as the tube sticking out. How much pressure are you using when casting? ( assuming you are using pressure ) I went from using 50lbs of pressure to 35 lbs or so and that fixed the problem for me. Some don't use pressure at all.


Harry
 
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Harry hit the nail on the head about the pressure, the material is not shrinking. Also when you put the stoppers in push them in and pull out on the edge of the mold at the same time to make the mold "wider". Check out Ptownsubbies video on this

Mike
 
I agree with Harry. To add just a little to what he said I seal eyerything with ca. Coating also became easier when I bought finishing bushings from Woodcraft. When I paint the tubes I use med ca to seal the paint and that fixed the wrinkling problem. If I'm casting someting porous I first use thin then the med ca. I also coat between layers. I paint the tubes then coat with ca. Then wrap the label and coat again. Good Luck
 
..why PP?

..I use Silmar41 w/o a pressure pot and w/o any problems! Just lucky I guess! Be well....Jan
 
Thanks for the replies.

1. I did not seal the decal/sticker with CA. That would explain that problem.

2. I cast these at 50psi. I watched the ptownsubbies video and he casts at 55-65psi so that still leaves me confused as to why the resin shrunk so much. I bet it was about 1/8 or more from each end of the mold.

These cast were the last of my resin so I just picked up some fresh stuff today. I'll try it again at a lower psi and without any tubes just to see if it shrinks as much.
 

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Doug, Ptownsubbies also has another video that shows you how to prevent this. At least he did a few years ago. I think it's one of the beginners video on how to use the mold. Hope it's still there.

jim
 
I have those same molds and have used them frequently but never used with pressure. No need for it. The amount of resin used is not much and if you heat the resin there is virtually no air bubbles. The ones present are so small and they rise to the top and I will again say Silmar41 is the answer. I thought those type molds collapse under pressure or deform. I would never use pressure with them. My opinion.
 
jttheclockman...He's using Silmar 41. It travels 15 miles from the manufacturing plant in St Paul, MN to the craft and arts supply store in St Louis Park, MN, poured out of drums into 1 gallon cans and rebadged. The oldest stuff on their shelves is not more than 10 days old at time of purchase. It sounds like the stuff he had was sitting on HIS shelf for a while and may have gone a bit wonky.
 
PSNCO said:
jttheclockman...He's using Silmar 41. It travels 15 miles from the manufacturing plant in St Paul, MN to the craft and arts supply store in St Louis Park, MN, poured out of drums into 1 gallon cans and rebadged. The oldest stuff on their shelves is not more than 10 days old at time of purchase. It sounds like the stuff he had was sitting on HIS shelf for a while and may have gone a bit wonky.
Click to expand...

I did not see that he said that any where. Not sure about that because I have and used resin that is 1 year old and have not had a problem. Yes fresh resin is nice but not always possible. I think it has to do with the pressure stuff. Now coating the decals is also a must. I like to precoat with resin before I cast. I then know if there is a problem I do not waste my time and material casting. Just the way I do things.
 
I think the resin I used was about 8 months old and it was the last of the can. Picked up another can today so tomorrow I will try a few experiments. One with pressure and one without.

I did precoat the barrels with the fabric on it with resin. I did not use anything on the red barrels with the decals. That was a mistake on my part.

I'm not too worried about the decal barrels but the fabric covered ones are pretty time consuming. I'd like to get this figured out because I have a bunch more of those to cast.

I'll keep you all posted on the results of my experiments:)
 
So I did an experiment today and am very confused by the results.

I started with about 3 ounces of fresh PR, stirred in some MEKP and then poured that into two cups. I proceeded to add the mica powders and then pours into two molds.

One was placed into my pressure pot at 35psi for 12 hours. The other was placed in my garage for the same length of time. Temps were pretty similar.

When I went to look at the molds tonight, this is what I found:
The mold without pressure looks pretty good (other than my finger prints on the still sticky resin :biggrin:)
The mold placed in the pressure pot again shows major shrinkage of the PR.:eek:

Any thoughts?
 

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I will say again I never had a problem casting in those molds without pressure. One thing I would mention, i think you should always add the color in the resin before adding the catalyst. I would also increase the amount by a drop or two per ounce if adding colors. Just my opinion. I do have some casts under my belt though.:)
 
Your mold appears to be changing shape under pressure, not the PR actually shrinking. I solved my bubble concerns by using a bit of styrene monomer in the resin. It helps it degas faster and more thoughly. It does take a bit longer to fully cure, but eliminating the need for the pressure pot is worth it. I only use the pressure for making waste wood blanks now.
 
79spitfire said:
Your mold appears to be changing shape under pressure, not the PR actually shrinking. I solved my bubble concerns by using a bit of styrene monomer in the resin. It helps it degas faster and more thoughly. It does take a bit longer to fully cure, but eliminating the need for the pressure pot is worth it. I only use the pressure for making waste wood blanks now.
Click to expand...
Such as this? http://www.amazon.com/Styrene-Monom...id=1434602771&sr=8-1&keywords=styrene+monomer

I searched local hardware chains but didn't see styrene... definitely interested in trying it though.
 
This is the product I've been using. I haven't noticed any clouding of the resin. It does cause it to take longer to cure to a non-sticky surface. I also use this to pre-wet stubborn powdered pigments. I use around 2ml per 30ml, it does seem to make a huge difference in the viscosity of the resin.

Another thought on the original post, if those silicone molds you are using were not cured under pressure they will have air in the silicone, even if it's microscopic, and that will cause the molds to change shape. Contact who made them and see if they do, they may not be intended to be used with pressure. I set one of my homemade ones (empty) in a vacuum chamber just to see what happened. Under vacuum the tiny air bubbles inside made the thing change shape. (think pretzel!)
 
I know this is not a viable option for everyone but for those that can do it I degas my PR in a vacuum chamber after mixing. A slow pour does not introduce any bubbles and I have yet to get one in any castings. My pressure pot is sitting in the closet all rigged up and never used.
 
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