1st mold - not great result. Need help.

[SWO]

This was my first attempt at a 2 pc mold for a Senko. I used Durham's Water Putty for the mix. I read a lot of posts and followed the instructions the best I could, but I'm not very happy with how this mold turned out. I ended up with a lot of air bubbles in the mold. I tapped the sides of the mold box and even held the mold box against the side of my vibratory brass tumbler to try to get rid of the air bubbles. I don't know if the mix was too thick, too thin, etc. As you can see in one of the close up pictures, there is even a crack along the length of one of the cavities.

Any suggestions would be greatly appreciated, thanks.

[Bogbaits]

When mixing the water putty I get it to a pancake batter consistency,when doing the first half tap all the air out or vibrate but dont vibrate too much,when you think you have all the bubbles to the top lay in your masters,after dried mix up another batch and brush the maters with the mixed water putty before you pour the second half,this stops the trapping of air around the bait,Your going to make a lot of molds before you get it down,just be patient,youll get it,it took me quite a few times before I got a system down.

[Vodkaman]

You will notice that most of the rising bubble problem, only exists on the first half mold. This is because the second half was bottom poured, so the bubbles rise away from the working surface.

It is a good idea to keep this first mold as the master and never use it for pouring. From this, pour a new half. From this new half, pour a second half.

Pro's solution is very important too, eliminating the edge bubbles, shown in your second half pour.

Dave

[HJS]

SWO - Its a start. I think I discarded my first couple of molds before I came up with a useable one. I guess I've made 14 or 15 now and I'm still learning.

Based on your pics I'd say your mix was too thick, maybe way too thick. Its hard to describe the right viscosity of the mix needed to make good, relatively bubble-free molds. Seems most first attempts end up with a mix that is too thick. As a result, the trapped bubbles can't easily float to the top to dissipate.

I use a medium, kitchen-type stainless steel mixing bowl, maybe 8 cup size. Depending on the size of the mold, I'll pour 3/4 cup ice cold water and 1 tablespoon white vinegar into the mixing bowl then add the dry DWP. (Vinegar delays the setting time by 2x to 3x.) I don't measure the DWP, I just keep adding dry DWP 1/4 cup at a time, then stir, until the mix looks right. Now, whats right??? Mine looks like pancake batter thats a bit too thin & runny. Its runny enough that its almost self leveling when poured in the mold. Just a few light taps on the side of the mold using my fingers is all it takes for the surface to get completely flat. HOWEVER, before pouring the mix, I'll let the mix set in the bowl for about 5 minutes or more so the maximum amount of bubbles can rise to the surface and pop. Vinegar will buy you that extra time. All the while I'm rapping the sides of the bowl as well as lightly bouncing the bowl on the counter top. All this agitation helps the bubbles rise. To help the surface bubbles pop I'll lightly pass the flame of a shop-grade propane torch across the top of the mix. Go easy with this techniques.

Also, I think you need a better pour hole. Yours looks too long and too small in diameter. You also need a more pronounced reservoir hole to deal with shrinkage as the poured lure cools in the mold. Sometimes I drill out both my pour hole and reservoir hole after the mold is totally dry and hard. I clamp the 2 halves tightly together before drilling the holes. See attached pics. In these pics you'll see with this mold I inserted pre-formed reservoir holes (using Sculpy clay) and then drilled out an extremely short (like 1/8" long) throat at the bottom of the reservoir hole.

And last, after the mold is totally hard, I use a hacksaw or 3-cornered file to make the vent slots in one side of the mold only, takes only seconds to saw in a neat vent slot.

[SWO]

Thanks for the feedback guys, this really helps.

HJS, those are some nice looking molds and baits. Thanks for posting the pics. I can see what you mean about the pour holes and vent holes. I'll open mine up.

I took another stab at it and this time the mold turned out much better. I think my mix was maybe still a little too thick, but I produced a useable Senko type mold without any bubbles in the lure cavity. I'll post pics of my first lures when I make them.

Another question - how long do you have to let DWP molds dry before I coat the cavities with a mix of Elmers and water?

[borderbasser]

I also noticed that you said that you had a crack down the middle of one of the cavities. I have had this happen before as well...especially after pouring several baits. One thing you might try to do to help this, is lay some strips of drywall mesh tape in the wet plaster to help bind things together like rebar in concrete. I have not actually tried this, but I would imagine it would help. Just make shure that it doesn't interfer with the cavites.

TJ

[Vodkaman]

That doesn't look like a crack to me. It could be the mold parting line on the original bait.

Dave

[SWO]

That doesn't look like a crack to me. It could be the mold parting line on the original bait.

Dave

Upon taking a closer look, you are correct Vodkaman.

[DonA]

You can get rid of the air bubbles by lightly misting the putty with ordinary isopropyl (rubbing) alcohol.

I use a bottle with a sprayer like this one works a treat