silvery patches in tube-in casts with PR

[pssherman]

I think I have discovered what is causing the silvery patches in my tube-in casts. I did an experiment where I coated the CA saturated braided sleeves and denim with different materials. I heated them in an oven and heated the PR before mixing (4 drops per ounce). I then left them in the pressure pot for about 16 hours. When I took them out some of the casts had the silvery patches and others developed the patches during the next few hours. The resin was still quite pliable and when I sqeezed the tubes (vertical casts) the silvery patches increased in size in some areas and decreased in size in others. This tells me that the patches are areas where the resin has pulled away from the cast tubes. I think I need to increase the cure rate and/or leave the molds in the pressure pot much longer so that the resin is not pliable when the pressure is released. Any comments or suggestions?

Note: My work area is 50 - 60 F so it is difficult to keep things warm. I use a paddle stick with a drill to do the mixing.

 

[jttheclockman]

My thoughts again on your use. Let me ask when you say coated CA on braiding and denim with different materials, what do you mean?? Have said a few times I do not like the CA use but that is just me. Next is you are flirting with too cold of temps. Poly resins like 65 to 75 degrees. next is buy yourself an old toaster oven. Does not have to be a good one. You can find at garage sales and also dent sales. I bought mine from Walmart as a dent sale and got real cheap. This is how I heat my resin. The more catalyst you add the more brittle a blank CAN become but not always the case. I use 5 to 6 drops in my mix and find that to be just fine and I cast 1" round molds. If you use color dyes you will need to increase cat. Mixing, not a fan of any type of electric drill mixing. You are adding air bubbles to mix. I mix by hand for about 3 to 4 minutes going both ways with a plastic cup rated for resins and popsicle stick. Making sure I scrape all sides also of the cup. The larger the pour the longer the mixing time. 16 hours in pot should have been enough time to harden molds. I believe your temps are holding this back and thus you need to leave longer under pressure or increase temps somehow. You can take molds out of pot and put in toaster oven to complete curing and remove sticky stuff. This is what I do. If you press on a mold that is not fully cured you fractured the bond and it will craze on you as you are seeing. To sum up I believe your temps are the root of your problems. As mentioned before moisture from items as well as humidity can effect the cast. Good luck.

 

[its_virgil]

I have NEVER had success using vertical casting with snake skin blanks using poly resin. I would assume the same would be true for using material other than snake skin. I'm not new at this. I've had one batch of 20 blanks come out fine and the next batch (Or 2 or 3) of 20 (exactly same prep and casting) blanks come out with the silvery coating as you describe. Epoxy works fine but epoxy has other issues.
Do a good turn daily!
Don

 

[jttheclockman]

As Don said sometimes you never will figure out what went wrong I too have had some casts just look like yours and have no clue. Same pour, same resin and same time in pot. I showed an example the other day of one I did not long ago but same effect.

 

[JohnU]

If your blanks are "pliable" they are not ready to come out of the tank yet. They need to stay under pressure until they are solid. Your resin cures from the heat it creates during the chemical reaction with the catalyst. If you store your tank in cold conditions during curing it will affect the curing process and time. I like to place my tank near a warm heat duct in the winter or in sunlight in the summer as the blanks cure. You have to remember there can always be something else contributing to the failure. You have to look closely at the item you're using. Was it "contaminated" by something before you used it. In this case, that fabric was washed with detergent, maybe fabric softener, or something that can contribute to the failure. Other factors are… glue type, resin brand and type, air humidity/ time of year, weather, age of resin, mixing technique, resin temp when poured, and more. It's all about ruling out variables as you proceed. I cast all of my "clear" blanks vertically. I've had more failures casting them horizontal. Also, Part of the learning curve is to take your blanks- apply them to use, turn them, assemble the pen and use it for a bit to make sure the blanks hold up and are not too brittle, the appearance is what you want (proper color, and amount of colorant) so they aren't under colored when turned thin, and or that the resin doesn't pull away from the object in
clear casts. Casting isn't something you just do with high success rates. It's a process you fine tune as you learn and understand your resin and other products your using. It doesn't happen quickly and can be quite an expensive lesson.

 

[Kenny Durrant]

I agree with ALL the above replies. A few things I'd like to add is the type of glue. If your using CA to glue up the braid and not having to cut your fingers loose my hats off to you. I like using two part epoxy for the braid material. It give me plenty of time to make sure everything is straight and looks good. This has been debated here before but my experience is that CA needs time to degas. I wait 3 days before casting. Epoxy I let set 24 hours. I use 6-7 drops of MEPK per ounce and leave under pressure for 12 hours. The blanks may be a little tacky but solid. I'll put them in the sunlight or just set in room temperature. With most processes your allowed some wiggle room and still get a good product. In your case you might have enough small things adding up to your headaches.
This would also be a good time to say Thanks to those that have helped me on the road to where I'm currently. I've learned a lot from several people hear. After saying that we also develop a process that works for us and not necessarily everyone. People are on here from all over the world so products as well as weather conditions very quite a bit. Take all the information and think about why or why not it might help or hurt what it is your trying to accomplish. Good Luck and Take Care.

 

[jttheclockman]

I believe John Kenny and I are saying basically the same things. They probably said it better but I agree with both said. Kenny makes other points too about learning from many on here who have been down the same path and greatfully share their findings. But as also said take all info and devise your own method and just keep trying new things but keep records of what works so you can duplicate. It is all part of what we do here and that is make pens. This is a section of that which involves casting. Some days are good ones and some days you wish you stayed in bed. been there done that. Good luck.