Plaster Molds Research Articles

존재의 내면 표현을 위한 실험과 모색 - 권진규의 건칠조각

This study considers the dry lacquer sculptures of Kwon Jin Kyu. To this end, it compares Kwon’s dry lacquer techniques to those traditionally used in Buddha statues, while examining the formal characteristics and art-historical significance of his sculptures. Kwon first became interested in dry lacquer, a material rarely used in sculpture, after encountering the works of Toyoichi Yamamoto in Japan. He began using dry lacquer in his works in earnest in the late 1960s, after returning to Korea. Kwon discovered new expressive possibilities in Yamamoto’s dry lacquer works, but was not interested in their smooth, shiny surfaces, one of the characteristics associated with dry lacquer. Rather than choosing the conventional dry lacquer process of creating a smooth surface by applying lacquer to imperfections caused by the release agent, Kwon mixed coarse materials such as clay filler powder or ground traditional giwa roof tiles with release agent or raw lacquer to create rough surfaces, showing a preference for achromatic shades such as gray and black rather than the characteristic brown tones of dry lacquer.BR Kwon’s dry lacquer works can broadly be divided into early and late periods, with the transition from the former to the latter occurring in 1970. It appears that he first chose dry lacquer as a material capable of overcoming the disadvantages of terra-cotta sculptures, which were both heavy and fragile. Kwon produced relief works such as Acrobatics (Gogye) and Homesick Man (Manghyangja) while gradually also beginning to take advantage of the lightness and flexibility of dry lacquer by producing sculptures of standing horses with long, slender legs. In his later period, Kwon discovered various expressive possibilities of dry lacquer while exploiting its physical strengths. In Standing Horse, a horse with a plump body rearing up on its hind legs, he uses the horse’s open mouth, face pointing up to the sky, and roughly-textured skin to give visual form to emotion. In Crucifix, he uses rugged facial features, sagging arms and rough surface textures to express the pain of crucifixion. In his later years, when Kwon’s health deteriorated to the extent where he was no longer able to create new plaster molds, he began using molds made earlier for his terra-cotta works to produce dry lacquer statues. He rendered the surfaces of these works extremely coarse, creating a mood completely different to that of the robust structures and elegance of the terra-cotta works. This was the result of mixing powdered roof tiles with the release agent and reducing the amount of raw lacquer, so that the hemp fabric did not stick. These dry lacquer works contain no trace of the structure of things that Kwon attempted to depict in his terra-cotta works; rather, they are powerful expressions of the artist’s mental state and subjective emotions.BR In sum, Kwon Jin Kyu’s choice of dry lacquer for his sculptures goes beyond the continuation of tradition: The material’s durability and damp-proof qualities gave Kwon’s works permanence, while he used its other advantages, such as lightness, to overcome the expressive limitations of his terra-cotta works. Dry lacquer also offered a working method that allowed Kwon to continue creating sculptures, unaided, to the very end, even after he developed health problems. But above all, Kwon’s dry lacquer works are significant in terms of art history because of their powerfully expressive emotional aspects – totally unlike the universe structure and realist aspects emphasized in his terra-cotta works – which embodied an existential awareness by effectively expressing Kwon’s own collapsing mental state in his final years.

Design cerâmico e aproveitamento de resíduos sólidos: desenvolvimento de porcelana a partir das cinzas de ossos bovinos

O trabalho apresenta a obtenção de cerâmica tipo porcelana a partir da incorporação de cinza de ossos bovinos, por meio de calcinação e moagem dos mesmos, desenvolvimento de moldes de gesso e testes com óxidos, resultando na vitrificação de peças cerâmicas em referência à culinária maranhense. Como resultado, foram desenvolvidas petisqueiras de porcelana. Diminuindo os descartes de resíduos sólidos descartados na natureza e inserindo posteriormente este conhecimento nas comunidades ceramistas do Maranhão, buscou-se contribuir para o desenvolvimento local utilizando o design.

Effects of paraffin external coating on the degradable flower pot made of sludge cake

ObjectivesThe researchers have tried to economically make a flower pot from sludge cake produced in paper mill industries for the purpose of decreasing its volume. The crude flower pot did not resist natural sprinkling of water or natural rain. The aims of this study were to clarify two hypotheses: (1) whether life time of a degradable flower pot on the ground would be prolonged or not by coating it with appropriate material, and (2) whether paraffin, material used for coating flower pot, would prevent the toxicity of sludge cake in it.MethodsSludge cake was mixed with soil. The circular plaster mold was used as a fixed mold. Three types of coating materials, paraffin wax, tapioca starch and modified tapioca starch were selected. Water durability test was performed with a water sprinkler. As the toxicological testing, leaching test and seed germination test were used using the paraffin-coated flower pot.ResultsIn the water durability test, the durability was different among types of the coated flower pot. Among them, the paraffin prolonged the life time of flower pot on the ground until 5 weeks at least and may be 8 weeks. The results of leaching test using the paraffin-coated flower pot showed that three heavy metals, lead, nickel and copper, were lower than the standard in Thailand, but the paraffin had no preventive effect on the leaching of the heavy metals from the sludge cake in the flower pot. The seed germination test showed no significant difference in the number of germination of Chinese kale and the length of its leaf from those grown in the plant soil, and suggested that the paraffin-coated flower pot seemed to have no suppressive effect on the seed germination of Chinese kale.ConclusionThe paraffin prolongs the life time of flower pot on the ground. Although it has no preventive effect on the toxicity of the sludge cake in the flower pot, the paraffin-coated flower pot seems to have no negative effect on the environment. This paraffin-coated flower pot has the possibility to reuse the sludge cake in the horticultural practice of growing the ornamental plant.

Manufacturing of new potential plaster molds for slip casting of alumina nanoparticles

Plaster molds were made using α- and β-forms of hemihydrate plaster as raw materials and melamine formaldehyde sulfonate (MFS) as retarder. Effects of plaster to water (P/W) ratio on physical and mechanical properties of the manufactured molds including density, apparent porosity, fluidity, flexural strength, and casting rate were investigated. Primary results showed that α-hemihydrate is more compatible with increased P/W ratio than β-hemihydrate, while the addition of MFS promotes β-hemihydrate compatibility with increased P/W ratio that provides the proper condition for changing the porosity and controlling the casting rate. For measuring casting rate, slips containing alumina nanoparticles were prepared with 35 wt% solid content using Tiron (C6H4Na2O8S) and polyvinyl alcohol (PVA) as dispersant and binder, respectively. Results revealed that the fluidity, density, flexural strength, and casting rate of α-hemihydrate plaster are higher than β-hemihydrate plaster. Due to the improved diffusion rate of alumina nanoparticles in relevant slips, the porosity of the plasters should be controlled in accordance with the nanoparticles size. Results confirmed that α-plaster molds have better characteristics in this regard. After casting in α- and β-hemihydrate plaster molds, specimens were sintered at 1600 °C for 2 h. Hereon samples cast in α-hemihydrate plaster mold showed higher density.

Correcting Poland Syndrome with a Custom-Made Silicone Implant: Contribution of Three-Dimensional Computer-Aided Design Reconstruction

Poland syndrome is historically associated with hypoplasia of the pectoral major muscle and abnormalities of the upper limbs. The authors propose an innovative procedure for correcting Poland syndrome thoracic malformations using three-dimensional modeling. Moreover, the authors evaluated aesthetic improvement, satisfaction, and quality of life after reconstruction with computer-aided design customized silicone implants. Since 1993, the authors have treated 129 patients for Poland syndrome. Before 2007, the implants were made from plaster molds; since 2007, they have been made using three-dimensional computer-aided design. Patient satisfaction was assessed using a standardized questionnaire, and quality of life was evaluated using the Medical Outcomes Study 36-Item Short-Form Health Survey. Lipofilling was performed in combination with computer-aided design in one-third of cases, and breast prostheses were required in 24 percent of cases. We found three exposed prostheses and two infections. Cosmetic results were excellent in more than 90 percent of cases, and more than 80 percent of patients were very satisfied or satisfied, with no significant difference between men and women (p = 0.382). The Medical Outcomes Study 36-Item Short-Form Health Survey scores revealed significant improvements in role emotional (p < 0.05), emotional well-being (p < 0.001), and social functioning (p < 0.001). Correcting Poland syndrome using a computer-aided design silicone implant fulfilled aesthetic and psychological demands, and significant improvements were seen in quality of life. The technique is simple and reliable and yields high-quality results, and three-dimensional computer-aided design has optimized the authors' reconstructions. Nevertheless, associated procedures and secondary corrections remain necessary to obtain optimal results. Therapeutic, IV.

Experimental and numerical thermal analysis of open-cell metal foams developed through a topological optimization and 3D printing process

This study focuses on the thermal analysis and comparing a lattice model and an optimized model of open-cell metal foams manufactured thanks to a metal casting process. The topological optimization defines the complex geometry through thermal criteria and a plaster mold reproduces it in 3D printing to be used in casting. The study of the thermal behavior conducted on the two open foam metal structures is performed based on several measurements, as well as numerical simulations. It is observed that the optimized metal foam presented less and non-homogenous local temperature than the lattice model with the gap of about 10 °C between both models. The pore size and porosity significantly affect the heat transfer through the metal foam. The comparison between numerical simulations and experimental results regarding the temperature fields shows a good agreement allowing the validation of the developed three-dimensional model based on the finite element method.

Effect of Water/Plaster Ratio on Preparing Molds for Slip Casting of Sanitaryware; Rheology of the Initial Plaster Slurry, Microstructure and Mold Properties

ABSTRACTIn the common industrial range of water/plaster ratio to make plaster molds for slip casting of sanitaryware (from 66 to 82 parts of water/100 parts of plaster by weight), rheology of the initial plaster slurry, and microstructure and final properties of the mold and cast body were evaluated. Working time or time suitable for pouring plaster slurry to make the molds with lowest probability of defects (before an abrupt increase in viscosity due to the formation of gypsum crystals), such as pin holes and incomplete filling of cavities because of poor flow behavior, was determined through viscosity curves as a function of time. At the highest water/plaster ratio, the optimum working time for making the plaster molds was found. As the water/plaster ratio was increased, morphology of the gypsum crystals was modified towards large needles, promoting an increase in the mold porosity (up to 11%) that enhanced the main property of the plaster mold, i.e. casting rate (up to 8%), without changing the properties of the cast body and with a slight reduction in compressive strength of the mold (1.5%).

Activated reaction synthesis of silicon oxynitride from silica and silicon nitride

This study investigates the preparation of samples with equimolar parts of silica and silicon nitride and the subsequent reaction synthesis of silicon oxynitride. The influence of the raw material and the processing parameters on the conversion yield was analyzed. In detail, the effects of the silica crystallinity and of the grain size of the silicon nitride were investigated. Furthermore, the reaction synthesis was activated by magnesium hydroxide or calcium hydroxide. The samples were prepared by slip casting in plaster molds. Firstly, the optimal dispersant type, a synthetic polyelectrolyte, was determined. For the batches with the finer silicon nitride the measured optimal amount was 0.6 wt%. For the batches with the coarser silicon nitride it was 0.18 wt%. From the cast and demolded samples, broken pieces were fired at 1550 °C for 1, 8 or 15 h in nitrogen atmosphere. The conversion yield of silicon oxynitride was analyzed by quantitative X-ray diffraction. The fraction of silicon oxynitride increased with extended holding time at the sintering temperature, by the use of fine silicon nitride, and by the addition of magnesium hydroxide as sintering additive. The silica crystallinity had no statistically significant effect. The obtained maximum conversion yield was 92 wt%.

Leon Despres de Cluny: um escultor oitocentista esquecido

The present paper aims to recover the figure of Leon Despres de Cluny, a French sculptor active in Rio de Janeiro between 1861 and 1881. Despite having received limited attention within current art historiography, Leon Despres de Cluny produced a vast amount of works, in collaboration with important groups and often by official commission, thus achieving the highest artistic honors. In addition to his artistic production, he was one of the most important art dealers of his time, as he was responsible, both by means of his commercial company and later individually, for the sale of collections of old plaster molds acquired by the Imperial Academy of Fine Arts of Rio de Janeiro in the second half of the 19th century

Prosthetic Reconstruction for a Patient with Partial Hand Amputation

ABSTRACT Introduction Partial hand amputations are one of the most common types of hand amputation. Provision of an aesthetic prosthesis with adequate performance can reduce negative social and psychological impacts of hand amputation. The aim of this study was to describe the fabrication of a silicone prosthesis for a patient with partial hand amputation. Materials and Methods Alginate impression was taken from the residual limb and donor hand. The thumb of the patient on the affected side was covered with a thin layer of silicone so as to not prevent the natural movements of the fingers. A thin layer of wax sculpted on the residual limb plaster mold of the thumb. Four metal wires were put on the residual limb plaster mold. These metal wires are temporary and, after the curing of silicone, are removed from within the final prosthesis to create a suction suspension and lightweight prosthesis. Result In this study, the prosthesis was designed and built for a 30-year-old woman who worked in a toy factory and had four fingers of her left hand amputated. Conclusion The patient was satisfied with the prosthesis in terms of appearance, weight, and color. The thumb function was not limited by the prosthesis. The patient could easily use her thumb while wearing the prosthesis.

A novel method for creating custom shaped ballistic gelatin trainers using plaster molds.

Simulation based procedural training is an effective and frequently used method for teaching vascular access techniques which often require commercial trainers. These can be prohibitively expensive, which allows for homemade trainers made of gelatin to be a more cost-effective and attractive option. Previously described trainers are often rectangular with a flat surface that is dissimilar to human anatomy. We describe a novel method to create a more anatomically realistic trainer using ballistic gelatin, household items, and supplies commonly found in an emergency department such as the plaster wrap typically used to make splints.

Apport de la conception assistée par ordinateur (CAO) à la réalisation des implants thoraciques sur mesure pour correction des pectus excavatum. Expérience du CHU de Nantes

Pectus excavatum is the most common congenital chest malformation and is a common reason for consultation in plastic surgery. Our attitude is most often a filling of the depression with a custom-made silicone prosthesis. The objective of this work was to evaluate the interest of computer-aided design (CAD) of implants compared to the conventional plaster molds method. We have collected all the cases of custom-made silicone implants to treat funnel chests in our plastic surgery department. The quality of the results was evaluated by the patient, and in a blind manner by the surgical team using photographs and standardized surveys. The pre-operative delays, the operating time and length of hospital stays, the number of surgical recoveries, and the post-operative surgical outcomes were recorded. Between 1990 and 2016, we designed 29 silicone thoracic implants in our department. Before 2012, implants were made from plaster chest molds (n=13). After this date, implants were designed by CAD (n=16). Patients rated their results as "good" or "excellent" in 77% and 86% of cases respectively in the plaster and CAD groups. The surgical team's ratings for CAD implant reconstructions were better than in the plaster group: 8.17 versus 6.96 (P=0.001). CAD implants were significantly less detectable than the plaster group implants. The operating time was reduced in the CAO group: 60.2 compared to 74.7minutes in the plaster group (P=0.04), as was the length of hospitalization: 3.5 versus 5.3 days (P=0.01). There were no significant differences between the two groups in terms of post-operative complications. The management of pectus excavatum by a custom-made silicone implant is a minimally invasive method that provides good cosmetic results. The design of these implants is facilitated and qualitatively improved by CAD.

Using Porcelain Replicas for Precision Control in Flintknapping Experiments

ABSTRACTThe experimental replication of lithic artifacts occasionally encounters issues of standardization and control. Two major issues are how to accurately create a large sample population and how to sample from specific stages over the flaking process. Knappable stone is unpredictable due to inclusions, cracks, and differences in size, texture, and fracture toughness. While this aspect of stone is critical to understanding some aspects of human behavior, decision-making, and skill assessment, in some experimental studies it may hinder other areas. Research for a large study assessing the failure of Folsom preforms during the fluting stage required many knappable facsimiles. The process outlined here uses porcelain as a medium for tackling these requirements. The new method presented here illustrates how a 3-D scanner and printer can be used to record and produce a copy of the artifact form. It then describes how to create a plaster mold of the printed artifact form and, finally, how to cast and fire the artifact replica in porcelain.

Assessing the Surface Distortion of Plaster Molds Made with the Use of SLA Models

Abstract The method of determining the accuracy of polymer molds in plaster forms has been discussed. Distortion of the surface of molds and plaster molds has been assessed. It has been found that the presence of monolithic and porous structure in the samples does not change the accuracy of the surfaces when forms are prepared for removing the material of the model. It has been found that in case of full-mold casting it is more expedient to form the mold cavity with cellular adjustable structures of molding prototypes.

Properties of Sintered Bronze-Graphite Containing Calcium Sulfate Derived from Waste Plaster Molds

This study examined the effect of calcium sulfate additions on the microstructure and frictional properties of a 95bronze-5graphite material, commonly used for frictional applications. The samples were prepared using a powder metallurgy process. The calcium sulfate powder was obtained from recycled plaster molds previously used for ceramic slip casting. The plaster molds were cleaned, crushed and ball milled to obtain powder, which was calcined at 400 °C for 4 hours and screened. 2 to 8 weight percent calcium sulfate powder was added to a premixed powder composed of copper and tin and mixed before the graphite was added. The powder mixture was compacted into a disc shape under a pressure of 500 MPa. The compacted samples were sintered at 750 °C for 30 minutes in a reducing atmosphere. It was found that the green density of the samples decreased with increased amounts of calcium sulfate. After sintering, the densities were found to have decreased due to sample expansion. A finer microstructure was observed in the samples containing calcium sulfate powder, possibly due to a grain boundary pinning effect. The addition of calcium sulfate resulted in the reduction of both the measured friction coefficient and wear of the bronze-graphite samples. However, the addition of calcium sulfate powder above 6 weight percent appeared to show decreasing effects.

Slip Degassing to Improve the Properties of Slip Cast and Reaction Bonded Si3N4

The effect of slip degassing on the microstructure and mechanical properties of slip cast and reaction bonded Si3N4 was studied. The slip was prepared by aqueous ball milling of silicon (Si) powder. Hydrogen bubbles, a result of Si oxidation during milling, were degassed from the slip using a combination of vacuum and heat. The slip was then cast into a plaster mould to obtain rectangular green bodies. The Si green samples were sintered in a nitrogen atmosphere at 1500°C to convert the Si to Si3N4. After that the nitrided samples were polished to dimensions of 3 x 4 x 30 mm. The density, porosity, flexural strength, phase content and microstructure of the sintered samples were studied. The results showed that the degassing process increased the slip density. After casting and subsequent nitridation, it was found that the average apparent density of the samples increased from 2.89 to 2.95 g/cm3, the porosity decreased from 52.9 to 49.5 %, and the flexural strength increased from 8.1 to 9.3 MPa, when the degassed slip was used. A microstructural examination showed that the pores in the samples were filled with whiskers, which most likely resulted from a vapor phase growth mechanism. The samples produced from the degassed slip tended to have fewer whiskers, due to the reduced pore size and volume. A comparison of the XRD patterns showed no phase differences between the samples. The appearance of Si2N2O, and SiC likely resulted from the reactions between O2 and C impurities with Si3N4.

Effect of preparation variables of plaster molds for slip casting of sanitary ware

A full factorial design was used to evaluate the effect of various preparation conditions for making plaster molds for slip casting of sanitary ware. We investigated the relationships between the processing conditions, microstructure, and final properties of the plaster molds. The results showed that the rheological behavior, and hence, the time during which the plaster suspension is pourable for making the plaster molds (before an important increase in viscosity due to the precipitation of gypsum crystals) were dependent on the preparation conditions. Variations in the chemical composition, pore size distribution, and microstructure explained the statistically significant effect of preparation variables (including the mixing time, water temperature, and water quality). Preparation conditions that promoted high initial viscosity of the plaster suspension (accelerative effect of the setting time) developed less porous structure in the mold that principally increased the compressive strength (16%, deionized water instead of tap water) and the casting rate (9%, water at 25°C instead of 38°C). According to the results are proposed optimum conditions to make the molds while avoiding unnecessary energy use.

Depth-of-cure of Bulk-fill Composites Cured in Tooth or Opaque Substrate

ABSTRACT Purpose To determine the effect of substrate on the depth-of-cure determination when using hardness profiles in a covered-slot technique and to introduce a new covered-slot method that uses tooth substrates. Materials and methods Three bulk-fill composites and one conventional composite were tested: Tetric EvoCeram Bulk Fill, Venus Bulk Fill, Filtek Bulk Fill Flowable, Filtek Supreme Ultra. The composites were light-cured in rectangular slots (2 mm deep, 2 mm wide) made in a plaster mold or an extracted tooth. The slots were covered with an orange glass plate during curing, leaving one end exposed for light-curing. After curing, the glass plate was removed and the sample was stored in the dark for 24 hours before Vickers hardness was measured as a function of depth at 0.5-mm intervals. Results were analyzed using two-way analysis of variance (ANOVA) and pairwise comparisons (significance level 0.05). Results The hardness of composites cured in covered-slot molds decreased with increasing depth (p &lt; 0.001). Bulk-filled composites cured in plaster molds had a slightly lower depth-of-cure than those cured in natural tooth substrates. Differences between the tooth and plaster substrates were significant at all depths in the “packable” bulk-fill composite (Tetric EvoCeram Bulk Fill), and were significant at ≥2.5 and ≥3.5 mm in the flowable bulk-fill composites (Filtek Bulk Fill Flowable and Venus Bulk Fill) respectively. Conclusion Using natural tooth substrates in the covered-slot method increased the depth-of-cure of bulk-filled composites in comparison to opaque plaster molds. How to cite this article Church BW, Tantbirojn D, Do T, Wells MH, Versluis A. Depth-of-cure of Bulk-fill Composites Cured in Tooth or Opaque Substrate. Int J Experiment Dent Sci 2017;6(2):68-73.

Study of the viability of manufacturing ceramic moulds by additive manufacturing for rapid casting

Additive manufacturing (AM) has been considered one of the best processes to manufacture components with complex geometries, many times impossible to achieve with traditional processes, such as moulds with conformal cooling. Binder Jetting (BJ) technology uses an ink-jet printing head that deposits an adhesive liquid, layer by layer, to bind a powder material that can be ceramic, metallic, or other, which allows manufacturing parts to be used in research and industry.The aim of this work is to study the possibility of using BJ to produce plaster moulds for directly cast metallic parts at a lower cost than with metallic AM processes, using different types of infiltrates and post-processing parameters to improve the mechanical and thermal strength of moulds in order to be able to cast an aluminium alloy. The mechanical and thermal resistance of moulds with a thickness range of 2.5-4mm were analysed, as well as the surface roughness of metal samples, and compared with those obtained by traditional processes. Although all the moulds had good heat resistance during the casting, some did not have enough mechanical strength to withstand the metalostatic pressure, especially those with walls of 2.5 to 3.5mm.

Shear Bond Strength of Lining Materials to Calcium-silicate Cements at Different Time Intervals.

To compare the shear bond strength of three different light-curing, flowable composites (Ionoseal [IS], Vertise flow [VF], and Futurabond NR + Grandio Flow [GF]) on MTA-Angelus [MTA] or Biodentine [BD] at three different time intervals. Freshly mixed MTA or BD was applied into 180 identical plaster molds. Three minutes, 15 min, and 2 days after mixing, specimens of IS, VF, and GF with standardized size and diameter were applied on MTA and BD specimens (n = 10 per material and time interval). Subsequently, all specimens were stored at 36°C and 100% humidity for 28 days. The shear bond strength was determined using a universal testing machine. Statistical evaluation was performed using multifactorial ANOVA and post-hoc Tukey's Test (p < 0.05). Multifactorial ANOVA did not show any significant influence of the combinations "lining material × time" (p = 0.257) and "calcium-silicate cement × lining material × time" (p = 0.241). Significant influences were detected for the interactions "calcium-silicate cement × lining material" (p = 0.000) and "calcium-silicate cement × time" (p = 0.009) and for the parameters calcium-silicate cement (p = 0.000), lining material (p = 0.000), and time (p = 0.008). The predominant failure mode of the restorative materials to the cement surfaces was mixed. Already 3 min after mixing, IS, VF, and GF achieved shear bond strengths on MTA or BD that were similar to those after 15 min and 2 days.