Quality of resin casted BJD

How to identify the quality of a resin doll/BJD?



As you know, creating your own BJD is really difficult. But making a quality cast resin BJD is a real challenge.

For more details on the BJDs manufacturing technique in casted resin you can refer to the article about Recast.

The resin casting stage is a fundamental moment in the manufacturing process.

Today, many designers are embarking on the extraordinary experience of making BJDs. The consumer is sometimes confronted with a multitude of offers without knowing how to analyse them.
We are not talking about judging people, but about knowing how to understand the differences between this or that product in order to make it correspond to one's expectations, desires and budget...

Some artists prefer to go to a professional casting company to get an industrial quality BJD, but individual artists can also offer what is called "artist cast".
This means that the artist casts the resin himself, with love, and under artisanal conditions. The big difference in quality lies in the techniques and materials.

On the other hand, a pro cast will never be able to imitate the love and attention to detail that an artist devotes to his or her creation, and the absolute certainty that a piece of the artist permeates an artist cast.


As each creator has his own level of requirement and competence, we will see the frequent defects visible on "artist cast" dolls, those which can possibly appear even in "pro cast". We will therefore teach you to identify the quality of the casted resin BJDs that you will have in your hands.

For this purpose we will divide these defects into different categories;

  • Moulding defects
  • Resin constraints
  • Technical corrections


1- Moulding defects

When you want to reproduce a doll by moulding, you obviously need a mould. This mould is created by the artist with silicone.
The impression of the BJD is taken and reproduced in resin. This material is a chemical compound that will catalytically react from a liquid/viscous state to a solid/soft state.
Any errors that are present on the moulds will automatically be reproduced on the parts.

It comes from the prototype

For example, if the prototype is not smooth before casting, the roughness will be reproduced on the copies. The same applies to every bump, hole and irregularity.
If this prototype is 3D printed and not properly sanded to remove the print marks, the moiré of the print layers will be reproduced identically on the castings, a scratchy effect will be seen.


This defect can therefore be corrected before the mould is made, afterwards it will be too late.


It comes from the mould

Silicone, as we have seen, is a difficult material to work with. Mistakes can come from the prototype's impression as well as from the craft process of making the mould itself.
If a piece of plastiline, or a "bead" of Vaseline, is inadvertently left between the different parts of the mould, this will create an unwanted impression in the mould too.
If the mould dries in an inappropriate position, (e.g. deformations of part A to part B), or is held with inappropriate tension during the resin pour, this will deform the impression of the part that is supposed to be poured. This is often where mismatches are created on the joints of resin parts. Depending on the degree of deformation the error can be corrected or not.



Finally, silicone is a viscous material, so when you mix it with catalyst, you incorporate air which creates small bubbles. Without clearing the mould, not all the bubbles will be able to escape and some will remain frozen in the dried silicone.



This creates a difference in density in the mould material. Large bubbles can tear easily and create new defects. Small bubbles will alter the surface creating an "orange peel" appearance. This is irreparable on the mould and the only way to alleviate the problem is to sand the resin surface.



This kind of defect is rarely seen in a professional casting because in the factory, the casting is done under pressure. The moulds are therefore more massive and with fewer openings, making this type of craft defect almost impossible.

2- Resin constraints

Polyurethane resin is a very unstable material and a health hazard. It should always be handled with adequate protective equipment.

This resin, in most cases, has a surface drying time of between 5 and 10 minutes. This means that you have to act very quickly, and this short time is the major constraint.
Just like silicone, when you stir the resin to mix the two components needed for curing, you get micro-bubbles in the product. Without a pressure pot to reduce these small bubbles, the resin will have dried by trapping the bubbles. Seen from the inside, it will look like a Swiss cheese:

The only solution to get rid of it is to get a pressure pot, which is expensive, not very practical to use, and not always one hundred percent efficient when you only have two hands and five minutes to cast a piece... Sometimes you have to accept the evidence, resin makes bubbles, and that's how it is!

YES but... it is up to the artist to find his own solutions to avoid them as much as possible, and to make those that would be visible or problematic disappear.


Visible bubbles

The easiest bubbles to inspect are those that are visible on the surface.



  • Technical problem: the resin did not flow into a part of the mould (trapped air bubble, engineering defect),
  • Mechanical problem: bubbles created during mixing, trapped during drying.

Two solutions are possible. Repair if they are in a place where this is possible, otherwise the part must be thrown away and remade, trying not to reproduce the error.

Small bubbles are unsightly and should be filled in finely to improve the quality and appearance of the product. Large bubbles can cause brittleness problems and should not be ignored.


But also invisible bubbles

A part with a BIG internal bubble is a fragile part that can break at the slightest impact.



Some bubbles are created because the mould is particularly complex. But watch out for hidden bubbles, often you only need to place the piece against the light to see them if there are any.


Finally, our friend the resin is demanding and sometimes a bit of a pain... Yes, if she doesn't like the weather or if she gets old, she can have unexpected reactions:



In this case, unfortunately, there is no solution, you have to throw away the failed part, and often the damaged resin with it.
You have to understand that the whole interior of the room is like a sponge, there is nothing to repair.

The creator is therefore a slave to these little bubbles. You have to know how to judge the limit of what is acceptable and what is not, what detracts from the quality of the BJD and what simply makes it good to throw away.


3- Technical corrections

There are "defects" which are unavoidable and incompressible because they are directly linked to the technical casting process. It is therefore necessary to intervene afterwards to erase these marks of the work.

This is the case in particular for the "entry and exit castings" and the "seam lines" which must be cut and sanded to make them disappear and obtain a finished part:



The quality of the sanding is important because the finer the sanding, the smoother and more uniform the surface of the doll.


First of all, it is more aesthetic and it will make life easier for the makeup artist who cannot work on roughness or unsanded areas!

In the case of "professional" casts, depending on the professional who does the casting, it is possible to find small bubbles and protruding seams in small quantities.
Some BJD companies have even chosen not to eliminate seams for economic reasons.


4- Finishing


The same applies to the finishing. In particular the gluing of the magnets, which some official companies have decided to do without.
Sometimes the magnets are sent unglued in a separate bag and the buyer has to glue them himself.

The installation of the magnets, their adjustment and even their inclusion in the resin are finishing services that take time.




You can also study the quality of the drillings, and the attachment system which is sometimes more or less practical (e.g. if the head can be removed easily or if the doll has to be unstrung for that, idm to change the hands/foot...)

Some designers offer "garbadge kits" or "B grade". These are lower quality parts at a lower price. Sometimes the doll is assembled with these parts, sometimes the kit is sold disassembled and it is up to the customer to sand if he wishes, and to assemble his doll himself. All this, once again, with the aim of saving labour and therefore offering a lower price on products of lower quality.

Other artists have the opposite approach, and even provide sueding work to make the posability optimal (sueding with hot glue or fabrics).


As for the make-up, it is sometimes supplied as standard, sometimes offered as an ooak or sometimes not available at all. It all depends on whether the artist is able to offer this extra service or not.
It is obvious that a unique make-up / doll in fullset ooak, brings an added value to the object compared to a serial service.

Premium service

Finally, all the additional services that increase the quality of the BJD, its uniqueness, its practicality, are to be taken into account. (Case, accessories, extra parts, fullsets, certificate...) Most designers offer certificates of authenticity due to the proliferation of counterfeits.

Packaging is more or less elaborate depending on the creators, their needs and their product range. There are two main trends: boxes: made of cardboard, wood, leather, etc., solid and aesthetic but cumbersome to store, and covers: more or less padded to protect while remaining easy to transport and store.


If we were to take stock, how good is BJD?

Now you are much better informed about the constraints of casting BJD in resin and their consequences on quality.
Let's summarise this in a VERY GENERAL table, and draw your own conclusions.


Quality Artist cast Pro cast Companies
Smooth surfaces / no irregularities
Good fit of joints / parts
No big bubbles / hidden bubbles
Very few small bubbles visible
Absence of 'foamed' parts
Zero visible seamlines
No sanding marks
Good finishes
Premium service (sueding, makeup, bag…)
Price range
Extra soul


To the artist's choice (technical choice, quality, marketing)

Options of the designer's choice (Options invoiced by the service provider)

Companies choice (technical and marketing choices)

(Please note that this table is not exhaustive and is given as an indication, so that you can form an overall opinion. It is possible that, on a case-by-case basis, you may find differences with the information listed in this table).

Let's keep in mind that every effort, every minute spent to improve the quality of a product takes time. More time and better quality also means an increase in the price of the product.

These are therefore crucial elements to consider when holding an artist's precious creation in your hands.