Better Scale Detail On Molds

Tahr, your resin bondo mix is often referred to as gel coat, but it is not. This combination will work, however it has drawbacks as you state. The bondo does two things. Thickens the resin and decreases the setting time. To make a quality production mold forget about that mixture and use true wax free gel coat, as that is what its made for. You can thicken your gel coat if needed with talc, cab o sil, or micro balloons. Even when thickened, true gel coat will disperse much better than resin/bondo picking up the finest detail. You can also shorten the setting time by using a quality MEKP like High Point 90 or setting it in direct sunlight. You do not need to use both hardeners in a resin/bondo mix like most believe is necessary. Resin itself is pre catalyzed and not photo chemically reactive. However, MEKP is photo chemically reactive hence using sunlight to activate the MEKP in the gel coat for a very fast cure. To prep your fish, remove all the slime with white vinegar and dry very well. Pose, then dry again. I then mix clear lacquer with the powder pigment used for color crayons. It is powdered wax that dissolves into the lacquer and is a superior separator for molding fish. I use the silver Venus #43 and apply with a touch up gun over the fish and shelf. The wax will show any and all moisture that would cause an issue in you mold. Mix and thicken your gel coat (wax free) if needed and apply. Set it in the sun, that should totally kick within 20 minutes. When set, you can coat again with either your gel coat or regular resin. From there you are ready for your matt application. This method will give you a quality production mold with great detail that will last many pulls. Hope this helps, and good luck

 

What do you molds currently come out looking like?

 

Put up a picture

 

Tahr, one of the many issues in using resin/bondo mix is the loss of fluid movement in your print coat that captures your fine detail. The thickness of that mix does not flow well and will capture any trapped air. Some air bubbles are expected as your resin/bondo mix catalyzes. You can see air pockets in your first picture. This is eliminated using true gelcoat due to it being much more fluid allowing your air to escape. Your barrier separator coat of lacquer/wax also eliminates trapped air because it is absorbed into the gel coat, and breaks the surface tension between your fish and print coat. For the amount of work invested in making a quality production mold it is important to use good quality materials made for critical molding and casting. IMO, forget the resin/bondo mix and use a good quality wax free gel coat along with a quality MEKP like High Point 90. For your barrier/separator coat mix, I mix in a pint jar 75% clear lacquer, 25% lacquer thinner and 1 table spoon of Venus #43 wax colorant (it is silver). Hope this helps, and good luck Tahr

 

Ahhh.
crab some of the best blanks around are molded out of bondo/ resin and cast out of bondo/resin.
However when I say bondo/ fiber glass resin the about of bondo I put in is only about 20% at any time. My first layer has the consistency of say rtv . It’s very thin in consistency and thickness.Bondo is pretty much just for the color.
Tahr you also have to remember your molding a fish that has tiny scales and in the case of that rainbow scales that slip extremely easily. There may simply be no scales there. And in the course of drying it out some scales are going to lay different then others. Salmon skinmount molds for example if done well look awesome anatomically and shape wise. However the scale detail can lack in areas as when a salmon dries out the scales lay extremely flat. think your mold looks pretty darn nice. I’d be far more concerned with the sunk in spots and the pose giving a very dead fish look.

 

Mudbat, as I posted earlier, many who mold fish use the resin/bondo method and I stated "it works". However, it has it's flaws like Tahr's post and the mold won't stand up to production molding compared to the true gel coat method I listed. The only reason the resin/bondo mix is used is for the decreased setting time of that mix and the talc in the bondo as a thickening agent. Your use of bondo as a coloring agent makes no sense when there are resin coloring agents for just that purpose. You can even tint your resin with acrylic lacquer. You also are left with the resin/bondo mix containing the wax from the bondo.
I find your statment "crab some of the best blanks around are molded out of bondo/ resin and cast out of bondo/resin"
I stated many use the resin/bondo mix and it works, however Mud please tell me what repo supplier sells blanks cast out of bondo and resin? Without the backup of cloth or matt, a resin/bondo cast would break just getting it out of the mold. I can think of no production fish blank suppliers that would ever cast a blank for sale using just a bondo/resin cast. Other than roto casting in plastic, the traditional gel coat layup method is commonplace in the industry

 

I have always just assumed mat or fiberglass chop was always part of the cast equation. No I know of no one who would do that without the added re enforcement. As for nice blanks that are cast in bondo/ fiberglass….
Dave Campbell, jimmy Lawrence, Rich Benedict, my own, etc….

 

Mudbat, without chop, matt or cloth as you stated your cast is weak and will break easily. There is no reason whatsoever to use a resin/bondo mix as the saturation coat for your layup material when straight resin is the proper choice. The use of bondo in any mix to lay up a blank is un needed and a waste of time and material. The wax in bondo will cause adhesion issues if not properly removed. I seriously doubt any of the people listed above make their blanks using bondo other than casting from the original fish. From our conversations on this thread it seems you are relativity new to fish molding and am sure some of the drawbacks and issues with the resin/bondo method will come to light as you mold and cast using this method.

 

Crab I will guarantee you they cast from their molds using bondo /fiber glass resin. Everyone also adds either chop or mat, because well it would be stupid not to. Either grey bondo (jimmy and Dave) or rich uses red bondo. It is mixed in with the fiberglass on the first layer. Just trust me on this one.
Pretty sure Dave at envision adds grey bondo as well.
That’s not gel coat that’s grey bondo mixed with fiberglass.
I use Bondo as a general term. As for me I use Evercoat brand resin and filler
You are correct i am new have only been molding and casting for a couple years. Learned the way I do them with the help of guys mentioned above.

 

I think the question to discuss isn't so much about who's who and what do they do. It's why.

Why choose a Bondo/resin shell over gel coat, and visa versa? Cost, availability, durability, temperature stability, ease of use, forgiveness, health risks, shelf life, cure time, inhibition resistance, compatibility, weight, etc...and...detail.

Just because great results can be had with both materials, rather than pointing out the anecdotal, it'd be better to know why those who are getting great results have chosen their specific approach.

 

Mudbat, your posts have alot of misinformation regarding the casting and layup of a fish blank. Evercoat bondo as is all regular bondo grey in color. There is no red color bondo. You are confusing the red glazing putty as bondo which requires no hardener at all. The hardeners for regular bondo are blue, white or red. The picture you posted is true white gel coat backed with regular lay up resin and matt, and is very easy to see on the shelf that contains no bondo at all. You would have to use so much white hardener in the grey bondo to make your print coat as white as in your picture it would set up before you spread it in your mold. There is no reason other than making a mold to use bondo in casting a blank. After 45+ years in molding fish and the use of many different materials and process's, laying up a blank is no different than making a boat hull. Not one major fish blank supplier would use the method you are stating and would be near impossible to lay up a large fish using body putty. I am quite sure when you cut out the mouth in your picture you will find resin and matt and no body putty

 

Crab not sure why your wanting to argue this. That blank is 150% grey. I know who cast it and I know exactly how it’s layed up. It’s a “gel coat) layer of bondo( white hardener/ fiberglass resin, the layers of fiberglass/mat. I use evercoat. Only the least expensive is grey. I use the mid grade and it is green. Ever coat only has blue hardener( atleast that all I can find).
Hop google and look at Dave Campbell’s blanks. Grey as grey can be.
Rich B uses red bondo hardener. He primes them white before he ships them. Scrape off the paint and they are red.
I know this about these blanks because they are friends of mine and I have worked on them many times putting my mediocre paint work on them.
All it is is a thinned down layer of a little filler mixed with fiber glass then layers of fiberglass/ chop or mat layers down over that. I’d imagine similar to the way you would lay them up using gel coat. No one’s laying them up solid. That would weigh a ton.
Blank using some ever coat filler.
Dave’s using some grey filler


And that LMB from above is one of Jimmys.two of rich B
You can see the red inside the crack at the base of the pec fin.


All layed up I’m assuming no different then you would when using gel coat just with a mix of filler/fiberglass then layers of fiber glass /mat on top of that.