two part cast

[micharms]

Not that I can come anywhere close to claiming that I've become proficient at casting but I'm up for trying something new to me. I'd like to do a two part cast of some bottlestopper blanks so that I can have a coloured portion on the bottom and then embed something in a clear portion on top. I just don't have any idea how to accomplish this. I would gather from some of my reading on here that bad things could happen if I cast the bottom and then wait and cast the clear on top of that after it has hardened. Any ideas about this would be greatly appreciated.

It is going to be interesting trying the casting these days anyway since the highs here are only going to 10-12°C and I have to do the casting in my unheated garage.

Thanks for any help.
Michael

 

[dkelley]

Hi Michael,
I do my PR casting in 3 parts when doing certain things like wrapped tubes, etc. I create a base layer first, then add the tube while filling the mold 2/3 full, then come back about 15 mins later and finish with the last pour. I add each layer when the previous layer is of a jello consistency. I pressurize after each layer. I have had no air bubbles in my blanks when completed. I know that most people do their casting in one pour. I have found that my three layer method works best for me. However, I'm always looking for better ways to do things. As far as temperatures, I couldn't begin to compare since I am in the Texas heat!

Does anybody else do their PR casting in two or three parts/phases?

 

[micharms]

Thanks Dennis. Hopefully it will warm up a bit to get me close to 70°F by next weekend. I might try one pour this weekend and once I've pressurized the pot bring it inside to set up.

Michael

 

[cozee]

Embedded casting can easily be done in two or more pours. Depending on the item to be embedded, as already mention, allow the the first pour to begin to jell. Place the item and pour the overlay color/clear. Since the first pour hasn't cured, bonding of the pours will be no problem as the solvents will still do their part.

Depending on the weight of the item, it can possibly float on the first pour without waiting for any jelling to occur. If one needs to make an immediate second pour, one can use a stake/prop of sorts to hold the item in place. After the first pour, insert the item and it's prop into the resin and one can then make their second pour. To help eliminate or cut down on blending of the fresh resins, pour the overlay down the sides of the mold and not directly on top of the first. Side pouring also helps to eliminate air bubbles. This practice works well when pouring the resin into the mixing container.

 

[cozee]

It is going to be interesting trying the casting these days anyway since the highs here are only going to 10-12°C and I have to do the casting in my unheated garage.

Thanks for any help.
Michael

Micheal,

A large cardboard box and a 60 - 100 watt light bulb makes for a great hot box even in an unheated shop/garage. Better yet, duct board (foam insulation that has a foil covering on one or both sides) cut and fashioned to make hot box. I use an old fridge and the 100 watt bulb can attain and sustain temps of up to 120°F (49°C) More than enough to get a good cure in a timely manner. You can also use this hot box to preheat the resin, pigments, MEK, and pressure pot if using one, to a desire working temp (around 70°F, 21°C). Even if one was to warm the resin and components and not use a hot box, curing times in cold ambient air temps would be more favorable. Just make sure the hot box is vented both at the top and bottom. This is especially a safety factor when not casting in a pot as the slovents can easily build up in the box and cause a possible volitile situation.

 

[micharms]

Thanks Greg. The objects have some weight so I'll try the first layer gel suggestion and then go from there.

As far as the temperature is concerned I have an old koolatron cooler/warmer that I;m going to use to keep everything warm until needed. Being a home winemaker I also have one of the belt heaters that you put around the carboy for fermentation. I was thinking about trying that around the pressure pot to see if it would make a difference.

Michael